My guess is the cannons damage being buffed, to let everyone more focused on

1) operate them
2) put adds under boss

All the fails I witnessed, saw all the time adds roaming the map and no one that arsed to move them aggros under the boss. Man, healers at a point will lose calm and forgot that the only ones to heal are cannon operators (if you don't esuna debuff they die) and tank.

Then, I still have to understand how dps can get aggro. Done (better: tried...) that as dps some times, and focusing the boss it is almost IMPOSSIBLE get any aggro from adds, they go to healers and tank. If you don't mindless aoe of course-.