My suggestion, reduce mana gained from Seal of Insight judges. It's firstly a really annoying mechanic to judge every 8 seconds costing precious GCD's to be our regen mechanic. Its totally out of line with other mechanics in terms of cost to us to use and how much we have to use it. Instead, take the 50% healing reduction off divine plea, buff it accordingly and make judgement mana returns significantly weaker but still useful, so we can still use it to stretch our mana if we need, but for those times when wasting a global is life and death, and were already burning mana like mad, we don't have to worry about killing regen as well.
So to summarize, divine plea is clunky and not in lines with other mana regen mechanics as is judgement via seal of insight. My solution is to reduce mana regen via the judgement mechanic and remove the mortal strike debuff (old school 50%) off divine plea and buff it to the point where paladin mana back is at a lower peak level but higher average due to being less dependent on judgment.
Also while I'm dreaming why not strike the 10% mana cost hike on the ptr off and use the changing of the judgement and divine plea mechanic to balance it out.