So how bad is deadly ailments righ now? I dont get it

It says that now the gem makes u deal 80% less damage with hits, it used to be 10% less damage. In a bleed build dont u inflict bleeding with physical hits? The bigger the hit the bigger the bleed damage?.

No, it uses your base dmg, the hit itself is irrelevant. This is a 0% nerf to pure dot builds

Actually, some DoT builds are nerfed by Deadly Ailment's nerf. Specifically, those who used Cruelty. Now, supporting Cruelty to a mixed skill (Flameblast, Explosive Arrow, Divine Ire...) would deal far less damage than before since the initial hit was not strong enough. This means that in order to take full advantage of Cruelty you need to resort to a pure Hit skill.

Of course there are pure DoT skills that are unaffected by all of this, but I think it's right to remember that Cruelty exists.

jewdas12 is correct, though. For your DoT, you use your base damage, and not the Hit damage. Likewise, you use your Critical Strike Multiplier for DoT rather than the usual CritMulti for scaling DoT damage from Critical Strike (so far, only Perfect Agony can turn critMulti into critDoTMulti. Damage over Time Multiplier is another thing altogether)

What do u mean by "my base damage" and "the hit damage"? I dont get it.

try this

https://pathofexile.fandom.com/wiki/Ailment#Damage_with_ailments