It is a handy power for taking alphas for a team, especially at low level (you get it at level 1). You jump in before anyone else, can gather them into a clump if desired, and then your team mates can open fire without taking the initial enemy attacks. You can't hold aggro hardly at all (once they get attacked, enemies will switch from you to who attacked them), but the mere going in first allows other players to do so much. Get off nukes safely, get off PBAOE controls easy, etc.
Later on there are better tools for this sort of thing (Controllers have pets now; you can IO yourself to high defence anyway, tanks can get in there and hold the agro, etc), but in the early game this is a really really useful power.