[Nick_K]

Regarding quickness:

AFAIK (from Dom2) quickness from spell or item doubles your actions and provides some other bonuses but does NOT stack with the 50% quickness from blessing - you just get the doubling. The maximum quickness most units can get is +100%

Heroic quickness, however, is special. Heroic quickness can give loads of actions. This stacks additively with the +50% from bless or the +100% from item/spell (or +100% total from both).
I've had units with four or five full actions per turn in Dom2. It's the best heroic ability IMO. Even better in Dom1 when the bag of winds could summon a free elemental every action...