That is probably a question of how one would like to carry out the balancing. In my opinion it is difficult to balance all classes in their combinations first and then to other classes because there is no real component that can be adjusted to make all secondary classes better or worse with one change. So I prefer to set a benchmark and then adjust all classes to the value. You would then have to decide whether you want to divide the classes into categories (aoe, support, single target damage, burst damage...) and how much you weight which category. (By that I mean how much damage can you "take away" from a class if it has good support skills.)
Well but that is probably an independent topic and is decided by the devs.
I think we are circling around for some days/weeks. Only a few classes get balanced atm, most is about warden and champ, sometimes a rogue appears in patchnotes (as I feel it). Imho balancing is not possible in the current content, since we have a too massive gap in the playerbase in terms of gear.
On one hand we got the (more or less) golden player raids which just destroy all inis and bosses in a leap. On the other hand we got guilds that still struggle on Inferno, Tikal, maybe Gorge. BUT we need a balancing that matches them all, or at least most of them.
The way how it's done currently is not the way I think it's effective nor efficient. Most players complaining about their very own favorite classes and are not objective, that's a problem. Also all our raids are completely different, in our guild runs the wardens are absolute overpowered, on others the mages, and so on. It all depends on so many factors, such as available support, gear, rota engine (custom lua, kitty, diyce, slayer, whatever). So that all makes no sense at all to me.
What we need is a unite environment to test stuff. On other games I saw dummy parses where you burst on a dummy to reach a specific amount of damage and check the time after that. Same could be done for AoE with multiple dummys. But ROFL is imho the worst example to compare classes/raids or to balance classes at all.