There's RNG heavy and then there's putting the player in the role of doing the background tasks while RNG itself is actually playing the game, and DD is far over the line into the latter. The one tool the player has to deal with the RNG in dungeons is the ability to retreat, which is penalized so heavily that it may as well be a fail-mission button. Unlike the notorious Dwarf Fortress, in Darkest Dungeon losing is not fun at all and really quite frustrating and you find yourself wondering why a heal spell that can be chain cast in battle indefinitely is bafflingly unavailable for use between battles. The combat RNG being heavy enough to kill a full health character before he is able to act in a battle - a couple of quite-common crits plus a third hit of any kind to deal the death blow can do that to any character - makes the incongruity of healing mechanics all the more glaring. Not to mention the characters will be going mad all the time and a common feature of almost all types of madness is refusing to be healed. The RNG is also doing the character development, by its Monty Haul assignment of significant traits. Rarely are the rewards from dungeoneering as significant as the effects of traits, which are applied to every character almost every time. So while your characters are developing, you the player though really have very little to do with it. You can alter these traits, but only quite expensively, and nowhere near the rate at which the game applies them on its own. And spending all your wealth to fix the traits on one or two characters does nothing to guarantee or even limit being RNG-slain in a manner that cannot be prevented with any player action or foresight. If you buy this game do so aware that it will be primarily for the production values, and that you will mostly watch and click along while RNG plays the game for you.
Evil Islands isn't flashy, but it was quietly one of the better RPGs of its time. Game play is fun and engaging and encourages creativity both in combat and with character development. A more interesting story than most, voiced notoriously poorly (at least in English version). As others have mentioned, do without party members since XP availability is finite and game play is simplified. I'd give it 4.5 stars since production values aren't good in a couple of places and the story could be a little longer. Really fun though, go play it.
This is definitely worth your time, however be prepared to work around the problem with combat, which is severe enough that it can ruin in minutes a well-played game that you spent many hours putting together. The combat problem is that the actual odds in combat bear no resemblance to the odds given by the game. You'll commonly encounter astronomically-improbable battle outcomes, and mostly these will be quite bad for you. At times, the game seems to decide that certain units will not be defeated, and anything you send against them will fail, no matter how many units you have at your command. My experience is that this can be worked around to some degree by choosing different attack squares or changing to a different attack then changing back (things that may give you a new roll of the random number generator), but probably you'll need to resort to save-scumming when this happens. Five stars as a simulation, minus one for a crippling problem with a key game element.
I would be the first person in line to buy this game at any price IF it were done right. I'd get my money back on this one if I could, and my time too. Lame AI, obfuscation as a substitute for depth, an uncomfortable combination of hyper-realism and too many things that require suspension of disbelief, all make for a game that didn't hit the target it was aiming at.
I've been playing computer games for almost forty years now, since the days of text adventures on monochrome monitors, and before that even, back to the days when the Atari 2600 was THE gaming system to own (Commodore owners' protests not withstanding). I'd have a lot of difficulty stating exactly which of the thousands of games I've played - RPG, RTS, strategy games, MMOs, shooters - is the second-best of them all. I have zero difficulty stating exactly which one is the very best. That one is Planescape:Torment.