My main suggestion is this:
(Numbers provided are mainly to provide perspective for my suggestions)
Make the Holy Power bar go to 500 and have Crusader Strike generate 100 holy power and have haste increase that by a corresponding percentage. Abilities that cast holy power would consume holy power in increments of 100 up to a maximum of 300.
The main reasoning behind me choosing the 500max/100increment numbers is that it would allow haste to consistently modify power generation as well as giving us a cushion for procs and giving us an outlet for some controlled burst.
Along with that remove haste benefiting CS and DS cooldowns and make give them a static 3 or 4.5 second cooldown.
Another thing to go along with this would be to have Divine Purpose cause the affected abilities to generate 15/30 holy power with a 25% chance to generate an additional 35/70 holy power. Smoothing out holy power some more, but still leaving some randomness in the Ret rotation.
Another big gripe of mine with Retribution's mastery. It's a cool idea in theory, but comparing it to the other masteries it doesn't fit. Ret's mastery causes a lot of rotation clashing as we already have a proc to use an ability and depending on when it procs it causes us to miss out on holy power and using other abilities. I think it would be better to have Ret's mastery passively boost the effectiveness of holy power, making TV hit harder, WoG heal more, and Inquisition last longer(this would still mildly affect rotation but in a more predictably way).
I would also like to hear what other paladins think, and what some of your suggestions are.
Please don't flame this, I want to try and keep this as positive of a discussion as possible.