I just tested frenzy barb as a rgk. I have almost 3k paragon and a pretty well geared frenzy barb with main gems on 150 and fully augmented gear. I needed almost 2min to kill a rift guardian without ads in gr 135.
As a contrast my impale dh with much weaker gear kills the same rift guardian on gr 145 in around 1 min.
Sanctified Wrath of the berserker is actually a very helpful group buff for your trash killer but you don’t have the damage for high gr rift guardians in reasonable time. And if you are unlucky and have to fight a rift guardian that spawns adds then it takes you even longer to kill anything.
If you are really determined to go for it and make it work and your teammates don’t have a problem with it then give it a try. I’d love to see frenzy barb as a commonly used rgk in high gr pushing