Stacking modifiers: Very simple, remove modifiers of Judgment and Final Reckoning, instead have them do other things that won’t provide a massive 20 or 50% damage increase.
Judgment ,consuming the Judgment debuff should simply cause your next HP spender to echo for 20% of damage, maximum of once every 5 seconds. This would enable you to get rid of bad talents like Templar’s Vindication and fix Tempest of the Lightbringer, which is okay as a talent but having to always watch 20 yards further than what you are actually trying to hit is not fun when pulling an extra mob could wipe your group in dungeons.
Final Reckoning, don’t scrap this, it should just be a big burst of damage and then either provide extra holy damage for every attack or something like 50-100% crit, so it still provides burst damage but not near the 50% amp it used to have. This would give Ret burst on 1m windows outside of Wings. The passive could also be changed to be active while it’s on CD and provide a free crit on HP spender or something.
Button Bloat: Seraphim, Divine Toll, and Exorcism all contribute to this while not being buttons you really care about or look forward to hitting.
Seraphim itself is pretty good but it’s not something you look forward to using or having to hit, it’s on the GCD, doesn’t do damage, it’s just stats, and that is okay, as a passive. It was best in SL Season 3&4 when you were able to maintain a large uptime while just playing normally. Buff Art of War to 30%, Buff Zeal back to 4 attacks and remove Seraphim as an active ability.
Divine Toll, nothing but a glorified Judgment on a 1m CD, without Ringing Clarity it doesn’t have the weight it did in SL, scrap it, replace it with Judgment cleave up to 5 targets.
Exorcism, sadly this ability is not what it used to be, so fix it. Blade of Justice and Exorcism should be options for your other builder, either ST in Blade of Justice or AOE in Exorcism. Art of War works on both, you make people who wanted Exorcism back happy, you help button bloat and you provide an option.
Survivability: Honestly this is probably where Ret needs the most help. First, make Divine Protection baseline, 30% 1.5m, make Shield of Vengeance a cheat death with a 150% HP absorb shield that does damage when it finally breaks, long CD 5m. Justicar’s Vengeance should provide healing or an absorb to your Templar’s Verdict and not it’s own separate spender. Take Bubble and Steed off the GCD so you can actually use defensives or movement when you need to.
Maneuverability: Would like to see an option of Speed of Light or Divine Steed, because steed is very ugly, but can live without as long as other improvements are made. Cavalier and Seasoned Warhorse should be 1 talent, make it 1 charge and extra 4 seconds of movement. The other talent should be an option between CD reduction based on HP spent like Fist of Justice or increased movement speed when you spend HP, 15% per point up to 3.
Utility: Absolutely nuke current Retribution Aura from orbit, NO BENEFITS ON ANY DEATH, simply make it 3-5% haste or mastery or both and now Ret provides a utility no one else does. Some other ideas, change Lay on Hands into a group heal and then maybe 10-25% damage reduction. Bring back group healing from Divine Storm, 5-10%. Put Divine Intervention back in the game, make it usable after 2 people have died 1 per group/raid only so you can’t simply use it to cheese mechanics like before.
Talent improvements: This was kind of not mentioned but lots of poor or dead talents in Ret tree, Blade of Condemnation, merge it with Expurgation. Improved Judgment, merge it with Highlord’s Judgment, 1 sec 8% damage, 2 points. Boundless Judgment, too much RNG already, delete. Seal of Wrath and Sealed Verdict, too little damage and too far over to warrant even trying to take. Templar’s Vindication this talent is horrible, RNG coupled with low damage, never actually worth taking unless you MUST get to Final Verdict. Execution Sentence, it’s just no longer fun or interesting, having to squeeze all your damage into tiny windows and pray you don’t make any mistakes or get mechanics is not good gameplay, needs a rework.
CONSECRATION: Something needs to change, either it needs to follow you or it should come off GCD and have a lower CD so you can drop it whenever you please. Static ground effects suck, especially during Sanguine or if a tank needs to kite, they are just outdated gameplay and need to be brought in line with current game design.