While i like the fact the op is trying to fix our problems in pvp as ret posting ideas here is useless because blizz cant read them and all you will accomplish its getting flamed by dipshits who dont know how the class works.
We have been balanced around having the complete immunity bubble since vanilla & frankly it isn't worth it anymore, 2 classes can break it 1 of which is the most common class found in arena setups.
Hopefully when next expansion comes they just remove divine shield & give us actual tools to work with because atm it isn't good for anything because every arena team makeup can ether get rid of it or force you to use it then kill your teammate while you heal yourself.
As far as things they could do once they get rid of divine shield, they could make the cool down on divine protection 2 minutes baseline, have the effect on glyph of salvation built into the spell, let exorcism have a built in 2 second interrupt since it has a 15 second cool down, let judgment of justice be an actual snare (maybe 20%), then give us some sort of small stacking healing reduction effect (possibly let crusader strike have a 4-5% ms that stacks 5 times).