You don't maul/melee every 1.5 sec. You use a GCD every 1.5 sec and maul/melee is mixed in there. Lets say you have 0 haste.
Originally Posted by Resilan
Over 7.5 seconds you 8 attacks, 2 that land at the same time. If you notice, the last attacks will reset the sequence so there is no need to go on further. You have to factor in avoidance/crit/boss attacks to figure out how likely it is to keep your bubble up, but I'm pretty that that it'll be up quite a bit. And because this isn't a sure thing (bad string of avoidance/noncrits), I doubt that they will drop our armor assuming it's up on every attack.
Attacks (in seconds)
Why are you so worried about trash? I don't take noticable amounts of damage during trash currently, and they stated that they want some thinking involved with Ulduar.