I really don't think it's a skill issue at this point.

Depending on what you were fighting and how you were going about each fight there are several issues I and others have come across.

The first thing is that mobs don't like being far from their spawn points... and by far... I mean a few yards. While fighting molting mitelings the other day my girlfriend and I could barely pull them out of their idle range without them giving up halfway through the fight to return to their territory, when this happened they dropped all previously accrued enmity and the enmity gain basically started from scratch, so whoever hit next had hate.

I've read similar issues with mobs that link, not being processed as claimed correctly for sections of the fight meaning certain people wouldn't be able to earn and keep tp long enough to use it.

I can't imagine these are anything but bugs.