I just can´t keep aggro at lv 50.

[SagaSoluna]

I had a quite easy an time tanking both dungeons and fates up to level 48 aprox but upon hitting level 50 i just can´t seem to keep any sort of aggro.

To make an example of what happened yesterday while fighting any boss at The Praetorium:

I would ask my party to let me get a few hits first, and proceeded to shield lob, savage/halone combo and used circle and spirits in between a couple flashes.

The very second the healer used one or two spells, the colossus turned tails and went to attack the healer, so i used provoke+shield lob and once i got his attention i began to combo...only to have the warrior steal the aggro in 3 hits and tank him for the whole fight, rinse and repeat.

In some bosses, switch "healer" for "black mage", the rest being the same.

Any idea of why this may be happening?