A cleric could maintain a full attack/heal routine for about 10-12 rounds of combat. According to various polls I've seen around here, an average combat at high levels lasts about 3 rounds, and people fight about 3-4 times per day, for a total of 9-12 rounds of combat each day. Thus, a cleric could heal itself about as often as the warblade could, and also has access to abilities like mass heal and all the various cure spells. Compared to a cleric of the same level, I don't think the warblade's ability to use the heal spell at will under certain circumstances is all that problematic.