Action Target Groups are the way to go. You can get fancy and have like Dps1 and DPS2 and have when you press like #2 for example it sends FTL to Tank1s target to DPS1 and FTL to Tank2s target to DPS2. This way you can split your dps if needed. Then have a all join DPS1 or whatever else you want to go back to the standard FTL setup.

Combine ClickBars with ActionTargetGroup toggles and you can make some very dynamic configurations. You could have seperate keymaps combined with action target groups for a specific boss encounter that work with a toggle. This was brought up in Mercucio's Deathwhisper thread.