As Nymrohd said, the Judgment mechanic is just poorly designed, and next to absolutely undertuned and/or badly designed talents Legion Ret just doesn't feel as fun as it used to. Our visuals even received a downgrade compared to what Templar's Verdict/Final Verdict were, only Consecration and Divine Storm look the part (and to an extend Divine Hammer), everything else is just "golf swing with a golden trail" now. The sounds aren't much better either. And visuals and sounds of abilities play a large role of the enjoyment of your class.
The complete removal of Seals and the replacement of Exorcism with Blade of Justice was a wrong move that hurt the class identity as a whole. Why not just change the mechanics of Exorcism, but keep the spell in itself? Also, the actual visual of Blade of Justice is too small for bosses to notice it, and it isn't unique either. The sword you see is just a reskinned
Fang of Twilight. Very lazy on Blizzards part I feel. The same argument can be said for Templar's Verdict.
To bring the spec back to a more enjoyable level something needs to be done. Either a complete redesign again (but who's to say that Blizz won't screw it up again), turn back changes you made during Legion or a complete return it to MoP/WoD.
- Judgment Debuff mechanic removed entirely, along with its mastery. Currently it doesn't feel rewarding, since for pure single target you can mostly ignore it entirely, and it hurts our AoE and target switching capabilities immensely. Personally I feel it's more hindering than Inquisition
- Hand of Light Mastery returned
- Shield of Vengeance replaced with old Divine Protection (damage on utility spells is a very bad design decision, since you will face the scenario of not having the utility spell ready when you need it since you used it for damage some time before, as for SoV's case, it's also possible that it won't do damage at all which is garbo)
- Arator's Leap ability added, perhaps remove Divine Steed for it (Divine Steed isn't a good ability in PvP since it doesn't brake/ignore snares). With DKs, we are the slowest moving melee spec in the game, and being so damn slow compared to everyone else jumping around is just not fun. Also, Tirion charged and leaped about with Ashbringer, and Arator's able to do it too. It's so disheartening to see your companion have more moves than you. Either that or LAotL.
- Consecration baseline (it's fine if it is dead last on priority or doesn't even go into <4 target priority damage wise, but an instant AoE without Holy Power cost should be returned. Also makes no sense for the other specs to have it baseline and Ret needs to talent into it)
- Repentance instant cast with a longer cooldown
- Hammer of Wrath readded (either as a "real" execute or with AW interaction
- Blade of Justice replaced with Exorcism in name+animation (the spell in itself can still be the same, but losing Exorcism really hurt the class identity in my opinion)
- Blade of Wrath talent (the old Art of War) baseline
- Desperately needed QoL stuff to increase the fun of the spec, e.g. Freedom can no longer be spellstolen, Retribution passive either removed entirely or the damage component removed, Judgment returned to where you don't have to face the enemy to cast it etc.
Some of this has been more or less asked for by the Paladin community over the course of Legion, but changes like that won't be done during an expansion. One can only hope that the devs will listen during the next alpha/beta phase when it comes to Ret's concerns.