It depends upon whether your group is going to be dropping appreciable AoE damage (e.g. there is a SMN or SCH who is going to DoT cleave, a WHM that wants to holy nuke, or a BLM that wants to drop some AoE hate) or going through the focus fire cycle.

If there is a lot of AoE DPS going out, I roll out with Tomahawk>Overpower>Overpower>SE combo(cycle it so that you get at least 1 hit on each target; this also gives you a good look at comparative enmity for everything). At that point, depending upon what the relative enmity of each of the enemies is, I'll either keep throwing how Overpower or I'll go into the BB>BB>SE combo rotation while cycling through targets to distribute enmity, depending upon the size of my enmity cushion on the non-"focus" target.

If it's a focus fire situation, I'll do Tomahawk>Overpower and then move into the BB>BB>SE combo rotation while cycling through targets to distribute enmity. If there are only 2 targets, the middle attack of each combo will hit the non-focus target. If there are 3 targets, the first attack and second attack will alternate between the two non-focus targets while the combo finisher will always land on the focus target (i.e. non1>non2>focus>non2>non1>focus).

In any case, if there are more than 3, you spam Overpower, use some CDs, and hope that your healer can keep up.

I should probably also mention that I don't use Flash, at all. I find it to be completely redundant since I already have Overpower, I don't have an appreciable mp pool, and I don't have any AoE enmity problems in the first place so I don't see the point in wasting one of my additional slots on an attack that I'll *maybe* use once or twice every fight, if that.