I tend to agree with the OP.
Yes, a shield tanked Gropho can be extremely powerful. No argument there, at least from me.
But, that requires prolonged coordinated key smashing in order to happen and if I wanted to spend my time key smashing I'd play a console game instead of perp - at least in a console game the coordinated button smashing has more intersting results. More to the point, I don't play console games beause coordinated button smashing is a PITA and not fun.
As for pve, the problem isn't that a gropho isn't as effective in pve as in pvp, it's that you have to waste a leg slot in order to farm npcs.
In pvp, even if playing a single account, in a group you can usually count on someone to rr you when your timing is off and the occasional hit gets through the shield. If you are doing pve solo, there is no rr. So, you either have to waste a leg slot on a repper (on top of the leg slot for the shield), or periodically go to the station to repair the armor damage that will slowly accumulate when your coordinated key smashing timing is off.