After experiencing some difficulty tanking PQs due to healers pulling agro, I did a bit of research. I found that one recommended strategy is to place the your guard ability on the healer in your group.
I tested this out while farming with Vwtifuljoe last night in DE Chapter 17 and it worked like a charm. Whenever he did get agro on any mob the I was able to pick it up with a single hit from any of my abilities.
I have yet to have the opportunity to try this out with larger groups, but will post with the results after I do. Putting the Guard the main dps'er is also something I intend to try out.
Just a small tip, but one that may be easily over-looked, especially since there was no ability like this in WoW... at least back in my day.