yes im able to fear ^^ mobs. the duration is short, but the recast timer is also. and generally i can keep an add occupied fairlyt well. only giants seem to be a pain only because targetting is harder when you have that much MOB in your face

as far as concentration. you have 2 windows with buffs. one is your maintained spells (you cast) and one if you general buff box. if you right click and cancel from the general box (where all your buffs show up) it doesnt seem to regain the concentration. but if you cancel from your maintained box (that only shows your buffs (or debuffs) you cast) it regains it 100% of the time for me. group or solo.