5 expertise is a sizable chunk, however it's not going to cap you. If you're the type of player that likes to see results, in recount i'm sure it will account for less dodges/parries, but you will still get dodged and parried. For that reason, I wouldn't go with expertise stacking unless I could actually hit 5% without sacrificing too much. It's just personal preference. I'm not going to notice a difference personally, i'll still be frustrated when dodges/parries occur.
Always remember to back attack targets, and targets who are spellcasting are i believe unable to parry (and possibly dodge.)