When attuned to a Berserker Weapon, if you receive damage and then fail a DC 15 Wisdom saving throw, you go berserk and must use your action to attack the nearest creatures (friend or foe), moving to the next creatures once the nearest ones are defeated. This therefore locks your action and movement.
But what about your bonus action and reaction? Let's say, for example, that I'm a Level 7 Redemption Paladin in berserk mode but with an Aura of Vitality, could I use my bonus action to heal my ally after the first hit, then use my reaction to take the damage instead of him (Level 7 Redemption Aura) on the second hit ?
Best Answer
Berserker weapons do not restrict how you use your bonus action
Rules as Written and Rules as Intended agree: you can use your bonus action freely while berserking.
Even though bonus actions are just a special type of action the fact that the item says "action" (singular) instead of "any actions you have" or "your full turn" means that it is only intended for the weapon to take up your one normal action each turn.
Also, the wording assumes that you are able to attack with this action every turn, this is not at all true of a bonus action in general and is more support that bonus actions were not intended to be included in the curse effects.
Jeremy Crawford explicitly supports this interpretation:
This also means that once you have moved and attacked you can move as you will as well.
But your proposed use of a bonus action still would not work
Jeremy Crawford has clarified:
You are taking the Attack Action and getting multiple attacks from the Extra Attack feature. However, you cannot insert a bonus action into the middle of another Action unless the bonus action says you can. The aura of vitality bonus action does not say so therefore you cannot do this.
However, you would be able to use the bonus action after your attack action was complete.
Reactions work as normal
Reactions are separated from actions and thus are unaffected completely by the curse's requirements.
For this case specifically, Aura of the Guardian states:
Since the trigger is taking damage, you can indeed transfer the damage onto yourself. You could even use this reaction between attacks if you wanted (unlike the bonus action heal as described above).