Enemy scaling should be universal, not tied to their aggro table.

[ArkTolei]

I don't ever play solo, and I find that the enemy scaling in multiplayer can be very frustrating.  If a new person hits a low hp enemy, that enemy is no longer low hp.  If a weak enemy visually aggro'd on 2 players instead of 1, it's suddenly going to take twice as long to kill.  If a player goes down, the party benefits from not picking them up, because any time you pick someone up, the enemy heals a ton of hp back from readding them to the aggro table.  It's a mess of exernalities.

I find that, on average, enemies are more difficult if there are more people attacking them.  That difficulty isn't "too high".  The game isn't "too hard."  I just want, when I get together with a friend, for them to be helping me, not hindering me 90% of the time (most enemies in mid-lategame have relatively low hp solo, the extra hp they gain from multiple players is rarely worth it unless they both start dps at the exact same time).  By that token, I feel that enemy scaling should be a flat boost to all creatures on multiplayer maps, that make enemies consistently more difficult, and make teamwork more important.

At the very least, enemy HP should not scale based on their maximum values, but their current values.  If you start with 100 hp, get it to 10, and another player aggros it, giving it a 20% boost to 12, that's fine.  If the player aggros it and brings it from 10 hp to 30, that's not acceptable.