I applaud the attempts to minimise the clericzilla tactics, but you have unwittingly made it easier for other forms of Divine Metacheese to be employed. Any priest with the Planning domain could start play with Divine Metamagic (Persistent). This allows them to make any of their buff spells last all day where they used to be rounds/level, at no extra spell slot cost (uses 6 turning attempts). The metamagic improvements need a rethink, but at least without heavy armor the priest will persistent buff the tank, not himself.