DoT and HoT seem to be working fine even if there are times when the second tick of an HoT or DoT is 3 or even 4 times what it should be. The heal on lycan was alternating from 575 to around 1600 in some situations. Dunno if that's meant to happen.
HoTs and DoTs can "crit" on the testing server, it's an intended feature, as it was advertised for when the void challenge bosses were released. It does so for self HoTs, enemy HoTs (presumably) self DoTs, DoTs, enemy triggered DoTs (presumably).
It's a mix of everything, the servers new damage modifier, damage boost items and Evo/Unlucky Leppy being well... buggy. They have been like that for well over 5 months now, nothing new.
I would just say you should use every class you have, it's free to use the auto enhancement button, so you can just put on 1 set and keep using the auto enhance button on that 1 set, you will have to manually enhance the items again once you return to normal servers.
Don't bother trying out TSS though, the damage is extremely low for some reason, only a couple 100 damage with full stacks before this update.
I feel like just increasing the players damage with a direct damage modifier is a bad idea, unless mobs and bosses also get some defensive abilities to at least even it out a slight bit (but not too much ). I like doing 4-5 digit damage per hit, it definitely makes me feel very powerful, but it just seems a tad extreme and we still have the very high crit modifiers, which just makes it even more crazy.
There's also some classes like Necro and Soul Cleaver who basically can't use their self damaging abilities without taking immense damage, or litterally just 1 shotting oneself.
Also a side note, the 7 Deadly Dragons are finally accessible on the testing servers, guess it would be smart for anyone who hasn't farmed drops yet, to do so, like Plague Knight items maybe?