Mobs can have a maximum of 60 icons attached to them, that's buffs & debuff combined (anything that creates a status icon). At any one time only 30 of these can be displayed. The other 30 will do damage or inflict a status but won't be shown. However, it's incredibly easy to reach that 60 limit depending on the team makeup. It's harder with 8 people, obviously, but once you hit 16 it's not difficult at all.