The bad part about letting other non tank class's wake them, is ussually chanter or cleric gets ate.
As for Memblur, I have a chanter, and although it seldom works, It can be usefull with major mobs, or when exact aggro chain needs to be made. It used to be used at times, for ensuring RT (Rampage Tank) Order was done precisely. These days, with mudflation of gear, and such, it's not as big of a deal. The spell itself isn't all that group friendly, as was pointed out, the refresh time sucks, Might as well let someone taunt three times as opposed to waiting for it to refresh. The Biggest reason however is simple. Chanter's don't have enough spell gems to keep it there, it's not an important enough spell to put in gem slot unless your with a bunch that don't know what they are doing. You need a slow, tash, Ruin, specialty slot (Debuffer, Cripple, etc.), Buff that leaves fast such as NDT,or even haste, A mana drain, then you have stuns, DD and DoT spells, that all help with group dps. I have different setup's for different zones. POI Dragon walk makes memm type spells very useful, but they aren't one of the best things a Chanter can have up in a good group.
Ruin will get you aggro if your Ruining the person that has the mobs attention, including yourself, however it don't seem to be that big of a problem. There are self ruins that don't cost Dot's, (Two, but on same line) and an AA ruin that stacks. The AA ruin is nice, cuz it's an instant Ruin, costing no mana.
When Chanter's are used in groups, people seem to be a bit lazy, and don't care if they get an add or two. This also effects the chanter's spell setup. IF you have two incoming mobs, I have to mezz one, slow it (Remember this chanter's, make sure the one that's definately gonna hit you if mezz wear's is slow'd FIRST!), then slow the one everyone's fighting, debuff, etc, then remezz to ensure it don't fall too soon, back to the one everyone is fighting, and help out, back to your mezz'd one, awaiting tank to aggro it. If you cast Memm blur after it's already coming for you, you won't get him off you, but you will erase any hate anyone else has built up (Ex": Pally stuns mob right before you Memm, stun is alot faster then Memm, so happen's), the stun isn't remember'd, but you standing right where mob is looking will effect who he is going to hit.
Aye, you need to chew them out if they break mezz before you get aggro.