I find it funny you start off your logic with the following but then complain that RPR, PLD, DNC, & BRD don't have enough carry potential. I know you said you're specifically referring to casuals and not vets but there's no way of making changes just for casuals without affecting the rest of the player base.
This is just like the PVE discussion. You're basically arguing for homogenization. What makes those 4 jobs you listed fun, in the context of FFXIV's most basic iteration of PVP yet, is that they require a little more testing out to master it. It's impressive seeing a RPR, BRD or PLD be top dmg in CC (DNCs have no problem). In crystal CC matches PLD & BRD are favorites.
Some people like choosing "underrated jobs" to master and by making them all easy to pick up for casuals (which I'd argue they already are = BRD is the go-to for new pvp players) you'd be removing this.