DLC definitely has some wacky bugs. One of the new artifacts (Fearfire Mantle) throws a LUA error every turn.
It's a shame, because it would be really fun with doombringer (all the fire).
RE: online payments. I've heard stuff about getting prepaid credit-type-things at stores, but I've never done it and they may or may not exist in your area. If you have any way to get money on to a Steam account (friend with a credit card?), you can buy the expansion there assuming you own ToME there. And assuming you're alright using Steam.
RE: massive beatstickery. Brawler is great. Muscle-wizard is best class. It's hilariously fun. It's not 100% guaranteed roflstomp, but it's a great mix of durability, mobility, and beatstickery. Key points:
- You can punch people so hard they explode.
- You can hit semi-indestructible enemies so hard they die anyway.
- You can put casters in a headlock and make them (silently) give you their lunchmoney.
- You can suplex entire rooms into submission. (see: muscle-wizard)
That and the abilities all work really well together (as in, functional and fun to use, not broken), and there's something really satisfying about getting a million attacks and proccing things off them all. (note that retaliation damage will wreck you.)
Allegedly one berserker build is supposed to be broken good, last I checked. But I found the early game so tedious and frustrating that it just wasn't fun to get started. :-/