Your combo sounds very situational, and that's not a bad thing, I tend to use tidal+AOE most of the time for openers, and once everything is flopping I target the boss for single target until the AOEs are back up. You build tidal stacks with certain attacks, and spend them when you get the orange ring.
One of the single target blasts does a tidal quick recharge. I'd put the Decimation build up proc in that power. Anything with kb can use a FF +recharge, but especially AOEs. Whirlpool is especially great for its proc options.
I leave Ablative Carapace on auto on pretty much every bio character I play.
As far as rotations? I would apply AOEs with secondary effects first, then do the same with ST.
I tend to push recharge on my heaviest AOEs but I pay for that in end cost.