Yeah if you don't need the Erudin faction and have the ability to kill there this is absolutely the answer. That's what I did on an Iksar when it was level appropriate, just go kill guards there (I think they're all level 30) and you will have the faction in no time.

The only downside is if you were trying to level off the lower level Paineel guards you miss out on that, but IMO there are so many better leveling spots till the mid-30s that this isn't really a problem.