I'm not too far yet (still in sewers), but I noticed an annoying issue when still in the arena.

When I tried to use crowd control spells such as Entangle or Web at long range, my party would immediately drop out of combat due to distance, thus speeding up time, and the enemies would just "push" their way through without me being able to shoot them/otherwise act.

It seems combat won't trigger until they're on top of the party.

Is there some way I'm missing to force combat mode to "stay on" so this doesn't happen?

I just shoot an arrow or a damaging spell/power. Doesn't have to hit.

One interesting tip: If you can get combat to end when there are still enemies alive, you can use the opportunity to heal up before restarting combat. Cell Adjustment is too weak to use during combat, but outside of combat you can repeatedly use it and walk back into combat fully healed.

On the other hand, psionic powers that need to be maintained need to be recast when this happens.