I have a barb and a cleric so I'm pretty experienced on how aggro works.
heal aggro is like damage aggro for the most part.
Note: all aggro numerical values made in the guide are completely arbitrary and do to not reflect the actual Numbers
If a mob has been initially aggroed (just by running into range) they will attack the person who triggered them. this is why u can pull a group of mobs in FC and run past your squad and not have any of them be attacked.
after a mob has been initially aggro it will then attack the person ho has the most aggro. so the initial aggro will be overridden by any damaging attack ( such as an aoe from a bm) and all the mobs that were hit will go from the initial target who ran to close to them to the target who dealt them damage.
whoever does the most damage will get the aggro.
here is where heal aggro comes in. walking past a mob effectively sets its aggro value to 1 for that player (the lowest # possible). any skill that deals damage will set it to a value based on the amount of damage dealt.
so lets assume the barb went and gathered 10 mobs, he then uses roar to set a high aggro value to those 10 mobs (assume roar sets it to 100). this allows the other classes to deal damage to those mobs without getting aggro until they pass the aggro lvl set by roar. (which was 100)
if i gather 10 mobs again with 4 ironheart precast on me, again all the mobs will follow me until another an aggro lvl is set above that of the initial aggro by range.
if the barb goes in and gather 10 mobs and THEN the cleric heals (after the mobs have seen the barb).setting the cleric aggro on those mobs to 8 all the mobs at were aggroed by the barb who have not been damage or have had their aggro value set above the initial value (1)will now attack the cleric who now has "heal" (8) aggro on the mobs.
in the same cause if a barb gathers 10 mobs and uses surf impact (a small range aoe) (aggro 15) which then hits 7 of the mobs. then the cleric heals. the 7 mobs the barb hit would stay on him with aggro lvl 15)and the remaining 3 which were not hit by the aoe and were still on the initial aggro lvl (lvl 1) will go at attack the cleric. (who has lvl 8)
so any time multiple mobs are aggroed initially ALL of them have to be deal damage (or roared) b4 the cleric heals or those who were not set above the initial value (1) will attack the cleric once it heals.
so u can cast ironheart on a barb as much as u like before he runs in. but as soon as he goes wihtin the aggro range of a mob. any further heals will set the aggro value(1 on the barb ) to a value (8) on the cleric during which they decide the cleric looks like more of a threat.
each player who hits a mob has his own aggro lvl for that mob. whoever has the highest one at the will be the target.
so lets assume we have a barb a cleric and a wiz
the cleric precasts ironheart. and the barb runs in.
mob sees barb and sets aggro on barb to 1
barb uses flesh ream setting aggr on mob to 50
cleric heals setting aggro on cleric to 20
barb does some normal attacks raising his aggro form 50 to 80
and cleric heals 3 more times raising heal aggro to 60
wiz then uses some skills and get his aggro to 75
barb uses ream 4 more times and sets value to 280
cleric heals and new value on cleric becomes 90.
then the wiz used BIDS and gets a crit and their value goes from 75 to 300
at this point the wiz now has a higher aggro lvl then the barb. so the boss decided to attack the wiz
barb seeing the boss running towards the wiz uses ream and sets his aggro on boss to 350
boss then goes back to attacking barb.
this also means that if the barb gathers a bunch of mobs the the big room at fc all the mobs will attack the barb (value 1) no matter how close they get to someone else.
but it also means that if cleric sets up blue bubble while barb has mobs following him and barb goes in bb range. the barb will be healed.. so.. now all the mobs following him.. will make a bee line to the poor little cleric who ins pretty much screwed unless another sqaud member can damage those mobs to draw them from the cleric.
so in short:
any damaging attack from a player will generate aggro on the palyer that did the damage
any heals done to a player will put generate aggro on all mobs who currently have an aggro lvl on that player. EVEN if that value is still 1
this also means that if ur wiz has the highest aggro on a mob 100 and the barb has 100 on another mob. but also the barb initially pulled the mob the wiz currently has so a value of 1 on the wiz's mob
the cleric healing the barb will get a aggro lvl of 8 on BOTH mobs.
meaning if the wizard dies..setting his aggro to zero the barb will still have an aggro lvl of 1 on the mob wiz's mob . while you have an aggro lvl of 8 from healing the barb. the mob will run after YOU when the wiz dies.
note: wings of protection (cleric skill lvl 79) does not generate ANY aggro. so if u cast that on a barb who is gathering mobs. (aggro value 1) they will NOT run towards you. and likewise will reset if the barb dies and not run towards you.
Killing level 80's with a lvl 60 is a lot more fun than killing level 90's with a level 100.