I think I know all the buffs (or at least I should have encountered all of them by now. almost 70+hours played on barb currently on act 3 inf. Not soloing though
)
I dont know if i'll be able to list single abilities and ways to counter them because its the mixture of the different abilities that make it really hard (Like you mentioned. Arcane/frozen/desecrate/molten + waller/jailer/vortex is a bitch if you dont have defensive/movement cds).
About the shields.
There are two kinds.
Shielding and Minion immunity.
Shielding makes the rare/magic champions immune to everything, including stuns/snares and you cant hit them for lifesteal. Shields go on and off automatically and I dont think you have to 'break' them to make them go away (not sure if you even can actually 'break' the shields. The intervals of it on and off didnt seem to be affected by my damage)
Minion immunity (i believe they are only on rare champs. Dont think that works on magic champs) makes the minions 'absorb' all the damage you do to it, but you can still lifesteal/stun/snare them.
Avengers was one I was not sure of until I met the 3rd or 4th pack of them in hell. They 'enrage' when you kill one of their members and you can see their 'bloodlust' type graphics on them. (can only happen on magic champs I'm assuming.)
I think the rest are pretty 'self-explanatory'
Illusions of illusionist mobs dont seem to actually have the special ability of their main body,(molten+illusion doesnt make the illusions leave patches of fire) but they still do normal attacks (and its a bitch if their normal attacks are special attacks, like the 'spider caster like' mobs that shoot ice/poison/fire at Act2 on the Zoltan Kulle dungeons. ESPECIALLY the fire one because they leave patches of fire that deal a shit-ton of damage).