I'm a fan of the master debuffer paladin. Planting the shield down will get you killed most of the time, so to stay alive use the Armor Boosting Energy drain and simply keep moving.
Energy Drain: Radius, Drain, Armor Boost.
Nothing in Incinerate (unsurprisingly)
Snap Freeze: Reach, Cryo Explosion, Damage & Weakness (I think that Tech Combo is good too!)
N7 Paladin: Damage & Capacity, Power Damage, and... prooobably weapon damage here. But keep your cooldowns low!
Shield Mastery: Durability, Shield Durability, Cryo Shield.
Snap Freeze is amazing and together with the Cryo Shield will bring down enemy armor to 0%, making it a boss destroyer.
whoa whoa whoa
The key thing about the Paladin is that you
need to have host in order to take advantage of the Energy Drain Armor Boost.
Also, the shield is amazing - but there are important tricks to the shield that many people don't know/take advantage of. When you drop the shield, you can block everything in front of you at I'd say for aboooooooooout 60 degrees or so (horizontal and vertical). You can soak up a LOT of gunfire with it, banshee bombs included. The caveat is rockets, heavy melee attacks (atlas, brutes mainly) will shatter your shield and knock you back a little bit. Its okay though because you can instantly redeploy the shield
this is important because it makes the shield durability a more or less expendable point to spend in that tree. You can redeploy a shield without any sort of cooldown. Don't waste the point.
Now, about shield dropping again - that cone is important. Because if your ass isn't covered, its the same as being out in the in middle of the street buttnaked.
What people ALWAYS forget is that splash damage from attacks that hits your nearby teammates will still hurt you. For example, you have some Rocket Troopers lobbing missiles at you and you're blocking them like a boss for the most part while some are going over your head - your teammates who are hitting that beacon objective are maybe 2 meters away from you and getting hit beside you. You WILL take that splash damage. The shield isn't broken. Its just not a bubble of invincibility like many assume.
Incinerate is pointless.
Cryo shield though... I'm not a fan of it for two reasons. 1) The armor reduction bonus on enemies it provides just isn't as good as it should be on higher levels. And the Flame shield provides a fuckton of more damage. 2) Freeze Melee is great for Phantoms, but honestly the class has so many tools for fucking up Phantoms (energy drain, snap freeze, the melee just wrecks them in general...) that you don't need to really to key on it.
I've always rolled with a Mattock w/ Incendiary rounds with the Paladin class because you can gauge the amount of damage you're doing as you set up tech bursts and explosions while maintaining a quick power recharge. You can deal out a very solid amount of damage at a distance when you need to without a scope - and now that you can slap melee dmg perks to ARs, it makes more sense to use and AR for this build instead of a pistol or SMG. Armor Piercing mod + Melee attachment w/ Incin Rounds. They key is to make an explosion or burst on every non-boss enemy that you aren't going to kill instantly with a melee.