In bear form, you get most of your threat from your weapon. Right now, you have good gear but your weapon is really low. Don't expect to be able to to hold aggro on ilvl 245 DPS class when you have a ilvl 200 weapon.
About youre rotation
AOE : maul + swipe and tab to make sure maul its everyone
Single : always queue maul, keep Lacerate at 5 stack and then use this priority: Mangle > FF > Swipe
For a threat boost you can use Berserk at the beginning of the fight to build some aggro.
But even with the best rotation, you weapon is too low to hold aggro on good ilvl 245 dps.
I hope it help