Daggers are only bad now that instant leech is gone and claws have life gain on hit, which means that claws are preferred over daggers for defensive reasons. But op has legacy acuity and a mirror tier dagger so it doesn't matter that it's a dagger build he's looking for. Should you need help with anything else in Path of Exile, you can go to U4GM. Bear in mind that if you need PoE Currency cheap, don't forget to collect more on this site.
Get an offhand stat stick and play phys reave or blade flurry. You can get some incredible damage that way along with solid life if you build it properly. As others have mentioned daggers are not the most desirable items to have, but having a ~600pdps weapon is going to compensate for that by a large margin. I'd probably pick pathfinder for consistency's sake, but you'd get more dps out of raider or scion maybe.
a. ES > life. You still have good ES gear available in std, but miss stand still faceroll. If want the stand still, get a (legacy) kaom and elder helm for 6 link (if you don't have the legacy kaom)
b. Pick a skill... lyco molten/blade flurry + stat stick etc. Depends on your helm and if you can get the molten enchant.
c. Even with legacy atzooby gloves - you cannot stand still and faceroll the uber fight coz of phased immunity - you still need to dodge and move around a lot (coz you won't always have a target to leech from)
d. Pick jugg - coz you already have insane dps. All you want is free tank/hp/regen. Extra dps (beyond a point) in the fight does not help coz you have about 45+ seconds of mandatory dodging due to immunities/phases.
e. Pick all life flasks - or alteast 2. Coz again, don't need the dps due to forced phases.
f. Obv get a legacy crit +phys ammy - those things are stupid more multipliers
g. Rings depend on choice of skill.
