I hate to complain and I know wizards offers the advice about jumping in and helping out a fellow wizard, but I would like to suggest that you ASK the wizard(s) if they need or want your help before jumping in.
In some cases, like random mob battles, all you are doing by jumping in is prolonging a battle. When you jump in, you draw in new enemies which makes things last longer. If you don't need to fight X number of a certain enemy, then there is no point in these battles lasting any longer than necessary.
I find it very annoying to get dragged into a battle while on my way somewhere, be almost done with the battle and then have another wizard jump in to "help" and drag things out even longer by pulling in more meaningless enemies.