To the developers -

MY EXPERIENCE WITH THE GAME SO FAR
I've spent about 20 hours so far, unlocked about 30% of achievements, been up to the Assassin and Watcher but beaten neither. (Tried the Watcher a few times, Assassin once).
I'm not new to this type of game, have been gaming most of my life (I'm 37), and think my skill level is probably about average within the group of 'life-long' gamers.
To me this game has brilliant potential - my favourite aspect is the crunchy & satisfying combat, especially on the earlier levels where it's not too punishing to get in amongst the enemies. I love the Parry move's risk/reward mechanic, especially how you can get health from it (with a mutation).
I particularly love the feeling of powering through the early levels, which is down to having learned the enemies' patterns and my own moveset.

ISSUES FROM MY PERSPECTIVE
1. The Watcher is too hard unless you grind up your gear. Getting to him is now quite easy - but beating him is far too difficult. The three times I've faced him, I made a solid build (stats & equipment), and managed to get his health down to about 30-50%. But the health bar is just too big - I can't see me beating him without grinding to level up my gear.
The prospect now facing me is to grind the earlier levels for upgrades to my equipment, so I can deal enough damage - or just walk away. I will try a few more times, but with approx 45min - 60min for each attempt, it's not that appetising a prospect.
2. The Clock Tower is not fun, and seems to almost actively discourage melee - enemies are so punishing that it's far more viable to just throw deployed skills down and wait until they finish. Especially when it takes quite a while to reach the Clock Tower in the first place (assuming you are doing the sensible thing and clearing out each level prior to maximise your gear & stats).
3. I really don't like that there's an option to level up your gear. That just looks like a hell of a lot of grind - especially because your gear loadout is randomised!!!! I get that it can make the game more accessible to people with less skill - but I think most of those people will just walk away rather than try to do all that grinding.

SUGGESTIONS
1. Give the Watcher considerably less health.
2. Reduce the number and attack strength of enemies in the Clock Tower.
3. Instead of offering the option to level up your gear (= grind), consider erring on the easier side for a player's first full playthrough, and then introduce New Game + mode or something, which ramps up the difficulty for people who have the skill and want to really challenge themselves. Rogue Legacy is a great example of this.
With the current issues, I think most people who pick up your game will walk away without seeing much of it, and probably end up unsatisfied. That's how I'm feeling currently.

I agree with most of what you said. Particularly about the gear level up. Having so much gear that is completely randomized just contradicts investing cells into a single piece of gear, which you might get or not. It would be more prudent if the guy to level up gear appeared after every level, after a point at which the player has unlocked most of the blueprints.

I suggest that you try carrying the Bear Trap power for the Watcher. It hard counters the charging tentacles and will help you stay healthy.

The Merchant Categories blueprint (found in the Graveyard) combined with the Shop Reroll blueprint more or less guarantees that you have access to whatever items you prefer to use. You do need the Spider Rune from the Slumbering Sanctuary to access the Graveyard. There is a harder mode available after you beat The Assassin (and harder ones after you beat both The Incomplete One and The Watcher in that mode). What you're playing until that point is what the developers apparently consider easy mode.

The Watcher is supposed to be a boss made for turrets, traps and cc builds while the Incomplete one is supposed to be for dps builds.
Same goes with clock tower, the alternative route, Forgotten Sepulchure is for dps/ melee builds.
And finally the level up system is not made ot beat the game the firts time, its made to be able to play the ng+ and so on that you should play only after having all major upgrades and the like.
And finally for the grind, i mean, even the trailer for the games kind of says its a grindy game, and it is, if you wnat to ease your grind by a lot, speedrun to all time doors you can, theese have level up scrolls and around 20 cells each or even more.

You know you can bash through the door after the collector to avoid spending your cells, right? If you use that, you can bring so much more to the foundry. Most I've gotten there with was 122 or something just rushing for timed doors, which is enough to get like four things from base to +.
And as others have said, the whole point of the foundry is for making an item merely viable for runs in the higher difficulties. Additionally, the last two of those "difficulties" make enemies drop insane amounts of cells compared to before, enough to even make the timed doors kind of useless.

I can't really add much to what the others have said. In order to make the game easier, you'll have to grind - but it will make the game easier.

Unlocking every single blueprint you collect will make the RNG work against you, so try to focus on upgrading your favorite items first before you start watering your useful item pool down. (Like Treadlight pointed out: Resisting the urge to spend cells at the Collector and breaking the door will enable you to save up plenty of cells for the forge.)

[Minor Spoiler!] In the Ossuary there's an enemy type called the Slasher (you can look it up at the statistic person at the start of each run). Slashers drop the blueprint for a Heavy Turret. If you want to unlock easy mode, try getting that. Especially The Watcher, the Clock Tower and the Assassin will get trivial with that one. However, you might not like what it does to your play style: I found that my main focus shifted to rolling around and dodging projectiles. I've just finished a lengthy nerf request for it, which should give you an idea of the benefits the Heavy Turret brings. (THat post contains spoilers, so you might want to Crtl+F for "Heavy Turret" and only read that section.)

Thanks very much for the helpful replies everyone.
After attempting the Watcher another 2 times I managed to beat it, and the Assassin I managed to beat on the same run I beat the Watcher.
I'd upgraded the Quick-Fire Turret at the Foundry, but that's it.
I also tweaked my run strategy - rather than clearing out all floors, I tried to quickly dash through for the timed doors, but if I found the end-of-level door early, I'd go back and hunt for a few scrolls before going through.
(This did require me to remember when the timed doors shut, so I knew how much time I had).

Probably the biggest difference for me was to realise the Watcher and tentacles don't actually hurt you when you're touching them - in other words, it's good to get up next to them and slash away. Previously I'd assumed (incorrectly) that touching them would hurt you. Don't know why I assumed that - probably from playing the eyeball boss in Rogue Legacy!

Anyway - this means I retract most of my OP. Seems pretty well balanced to me. Fantastic game - can't wait for the full release! But until then I'm looking forward to exploring some of the other areas I've not yet been to or beaten (just got the Spider Rune on that same last run!).

Nice to hear that you did it simonjameshobbs :)

In a few days or weeks you will laugh, when you remember that there was a time when you thought of one of the bosses as difficult. This is the great thing about Dead Cells! The games mechanics work wonderfully and you will always see progress in your own skills. Upgrading the gear is nice but an experienced player can beat his way to assassin with starting gear if necessary (at least on normal difficulty)

2 Month ago I thought the incomplete one as unfair when he killed me the second time. Now I do runs with 3 Boss Cells active and still enjoy the game.

Keep on playing, its worth it! (even with some balancing issues in the equipment. Some gear definitely is much stronger than other)

Dead Cells is definitely a game that rewards spending time improving your own mechanical skill as well as paying attention to the environment and enemies. Experimentation is also highly recommended, as you can often find some combination of items that work wonders for a situation you found difficult with your "comfort loadout".

In the Brutal update I almost always tried to go heavy in on Survival with a side order of Tactics, focusing on Shields and either Broad Sword or War Spear. In the Foundry update I have had far more success with the Explosive Crossbow and an Ice Bow + Turrets while going all in on Tactics and balancing Brutality & Survival (for the health boost). But each of those setups took me some experimentation to find.