With the 2 set buffing archangel to insane levels (10% crit, sup?) you want to use it on CD, which means that you'd probably have roughly one use with zero (right after AA popped), one use with 2-3 stacks, and one use with 5 stacks .
That said, when you consider such small things like average archangel stacks, then you should also consider mindbender's possibility to not get all it's hits in (dying mobs, moving mobs), it's more severe cooldown punishment for delaying, and the fact that it provides a ton of mana at once, while solace is a little mana every so often. If you have a tide, hymn, whatever going on, the chance of overcapping mana with mindbender is much bigger than solace =P.