If you want to, you can switch to Focus (Concentration).

The cap needs some work. It's a useful ability, sure, but feels like it's something that an out-of-the-box gish PrC would learn sooner in game terms; you should consider making it more of a meshing of casting and attacking you have building up while granting Combat Casting for (Heavy) Armor - I've always liked the idea of casting a touch-range spell with a successful melee attack, and you have that, so...consider allowing them to unleash any touch spell spontaneously with any successful melee attack? I'm not sure, but consider granting the 'Dance' to 5th level and developing a slightly better capstone - one that would warrant missing a final spell level.