Berserk is awful even on a mage, especially solo. The one that gives +20% dmg if not hit for 5 seconds is decent though.
Hidden blades on hit if you want to break the game.
Guard on hit is ok, I've discovered that there actually is a 1% heal on hit mastercraft (snoufler skin), which should be much better imo. That means EB = 12% heal or even 24% heal with static cage I guess. Couple that with ice armor and that would make KE and Champion look squishy.
Acually the more I think about it the more it seems that an ice build could actually work on RM. Weakness + Blizzard = constant mana regen, with snoufler skin it's also a health regen and ice armor gives awesome DR. Can make an aggressive close quarter RM build that charges in with fade step, pops up blizzard and proceeds to mess everyone up with stone fist and other damaging skills in his arsenal. Sounds like fun.
Walking fortress, Walking bomb and Shield bash procs are not bad, but not on the same level as the stuff above.
-20% ability cost is nice, but not so much for RM.
For staff, critical crafting is one of the best options (unless you really want to cheese hidden blades).
I used to run my main with guard on hit (health on hit would've been better in retrospective, never found it though) and critical crafted staff while Solas got 2x hidden blades and then got kicked out of the party for ruining all the fun.
For soloing I would say survivability mastercrafts look more attractive than dps ones. So probably 1% heal on hit for the armor and critical crafting or Walking fortress on hit for the staff.