My shiradi sorc's concentration sits at ~75 right now with no specific effort put into it. I'll likely be ditching my guild slot goggles when I rearrange my gear, so that'll drop to ~60 with no +13 item.
Concentration is greatly useful in EE. I only quicken Reconstruct and Otto's in EE; spells and ranged do not hit me for enough to interrupt my offensive spells any noticeable percentage of the time. Melee hits are rare enough to not care about, and I'm going to be more worried about Reconstructing myself afterwards anyway.