First, we remove his 1, then shift everything to the left, making room for his new ultimate.

Why? What is wrong with this ability that you would want it removed?

His 1 is now Hallowed Ground; it is changed to an AoE that functions similarly to Nezha's firewalker, in that it leaves a trail of hallowed ground wherever Oberon walks, and has a 25% chance to proc radiation when an enemy enters it, but it no longer does DoT.

Usability-wise, this is worse. I prefer a cast once method to having to run around to cover the same area. Hallowed Ground certainly needs changes, but this is not one of them.

His 2 is now Renewal; this will effectively remain the same, but will continue working when your teammates are at full health. It will now also cleanse yourself and allies of all status ailments, but only when they are at full health. (Effectively this means that Renewal has to heal your teammates fully before it will cleanse them.)

Renewal already removes status effects when at full health.

His 3 is now Reckoning; This ability will remain unchanged, but will have slightly reduced damage and energy cost, and the chance to proc radiation is reduced to 50%.

Why? The radiation is the best part of the ability.

His 4 is now Paladins Armaments; Oberon summons his Paladins Armaments, which are a shield and a mace (think a smaller magistar), which will benefit from melee mods. (Will not be based on base damage of equipped melee weapon) (Does not send out waves of energy like Exalted Blade)

Once again, why? Why should Oberon have yet another channeled weapon? Perhaps a shield-type system would work, but not another weapon. What does another weapon bring that's actually new?

I'm sorry if this comes off as overly-critical, but sometimes I really have to wonder if any of the people posting these Oberon rework ideas actually play Oberon regularly. So many of these try to make him into something completely different instead of improvements.