Seeing as my excitement is ramping up for the impending arrival of book 2, I present you...
The City and the Dungeon (and those dwell and delve within). Alex Kenderman, the main character and team leader is a healer with a drain heal build (why only heal, when you can heal using the mob's health pool).
All the Skills has classes that unlock based on which skills you manage to earn, and the MC, being able to collect "all the skills", has a large number of classes, which he switches based on what he needs at a given moment.
The City and the Dungeon has all this complex class progression that requires increasingly complex requirements, and you have to take intermediate classes to unlock the one you're aiming for (it inspired me for one of my series). Beware, no blue boxes/explicit descriptions.
I will note as an aside that https://smile.amazon.co.uk/dp/B08GYJ7BJ7 The City and the Dungeon is based on nethack. (loosely).
Including such things as conducts (avoid diagonals), teleportitis, mention of #elbereth, and most strikingly to me, a term I coined 15 years ago on IRC, 'dig for victory'.
I think this is the one they're talking about, gonna check it out after I finish shadeslinger