So lets just say the opponent is Lazu with Revites and Cosmo also in revites. Both are in same range.
Who'll proc first?
Attack speed is something which is mostly deciding who will proc first. We need to remember that insignias, talents, buffs from other heroes, enhancements, pets can also affect it. So even hero with 1200 attack speed can proc first, before hero with 1000 attack speed, if he was buffed by Michael or Athene for example, or had zerk insignias. And with all of those factors it is hard to tell if our hero should proc first, cause there can be many factors which will make that hero proc little later, which is enough for enemy hero to proc first.
It was easier earlier. Only Zerk decided who was procing in first order. Nothing else. Now there is much more to deal with.
If 2 revitalize heros h2h the auto proc hero Will proc first
But in team work it's another thing , and it depending on a lot of things. Like.... for example
if the opponent have 9/9 scatter in his team
Silence pets / debuffer pets
Attack speed will effect who procs first. A good way to get your cosmo to fire off quickly is to use uf5 as enchant. Also there is hero priority order to consider in lbf, lab, and arena. The way the game decides who gets hit first is based of your heroes priority. Each hero is different, and I mean if you level 4 cosmo's and max them out each cosmo will have a different priority. If you go into lost realm and make a team with mini ang pet, the hero that gets shielded by him is #1 on your priority order. So take that hero out of your lr team and see who gets the shield next. This is important because you don't want your cosmo to be 1-3 in order because your first 3 heroes get hit by the warden at the beginning. If you are facing a lazu I'm guessing there is an oracle warden too. If your cosmo is 1-3 priority then he will be silenced by the oracle warden right off preventing him from procing.