It's not this release because it's the exact same code as the original.

Levels are randomly generated. Sometimes you get unlucky. The Caves can be particularly nasty due to a level generation flaw. The level generator tries to avoid placing monsters "too close" to the entry stairwell. However, fenced rooms are special, so it has no problem placing a fenced room "too close" to a stairwell, then putting monsters in the room. This allows the monsters to be closer than they should be. As soon as you enter the level, the monsters go on alert and attack.

How far from the stairwell did you go before the monsters found you? How many, and what type, are they? Is there any terrain you can use to shape the battle?

As mentioned earlier the caves can often be a big jump up in challenge and difficulty, most notably level 10. When you run into this kind of situation it is best to leave the game and create a new one... and continue to power your character up somewhere a bit easier until your ready... your goal here is to get to level 20 so you can unlock nightmare difficulty and level up in the church. After doing this a bit you can then Return to normal difficulty and the caves should be significantly easier.

A character development guide I have personally found quite helpful:

https://d1legit.com/2019/03/29/diablo-1-get-godly-quick-character-development-and-item-finding-guide/

Those statistics may not be very good here. You don't say what monsters you faced, but picking a random sampling of the ones you might face, I'm seeing enemy AC in the 30-70 range, giving you an effective chance-to-hit of (81% + 17 + 20) - ([30, 70]) = 88% for the poor armor enemies (which is pretty good), but only 48% for some of the more dangerous enemies. Missing every other swing will severely hurt your damage output and make it unlikely to stunlock an enemy. Enemy HP could be up to ~100 (Flayed Ones, which also have AC 70), so you would need a minimum of 4 nearly max damage hits to kill a Flayed One. Monsters heal over time, so if you don't deliver your hits quickly, the enemy may heal back a meaningful portion of the damage you dealt.

Enemy CTH varies from [60, 100]. Enemy Final To-Hit will be (30 + [60, 100] + (2 * ([13, 20] - 17)) - 45 = (90 + -8) - 45 = 37 for the weakest, but = (130 + 6) - 45 = 91 for the strongest. If you're facing a monster in the latter group, you will spend a lot of time blocking, burn through hit points quickly, or both.

Thanks to all who replied. I finally managed to get a little breather and managed to determine that my main problem was a named monster in with the mob of standard level monsters. A combination of the town portal lure and flat running away via a level retreat let me clear out the standard guys so I could focus on the uniques.

Working on level 13 now.

Thanks, again,