Pyromancer–specifically the Pyro3Kino3Sage2–is actually a popular choice. But between Pyro 3 and Pyro 2, the only real difference is whether you want to take Hell Breath. Hell Breath on its own is pretty good but unnecessary so you’ll have to weigh it between getting 3-4 other skills from RC.
RC gives you two damage skills (RoD and RoJ), and a spell which gives both Interrupt- and KnockDown- immunity so it tends to be important for content that needs it, like Velcoffer, if that is your goal. The good thing about Rune of Protection is that it’s shareable but you’ll need Linker to do that. That, and aside from Hallucination it’s the only source of KD immunity on the Wizard tree if you don’t count Gazing Golem cards. The damage spells, on the other hand are fine. Even on my Shadowmancer, I still use Rune of Destruction as one of my main sources of DPS.
As for Pyromancer, I wouldn’t say that the class is ‘gimped’ but given its rank level it does what is expected of it. However, it will be better if you see it as a peripheral if useful source of damage. There is a lot of synergy between Pyro, Kino and Sage although to be fair it would typically be bested in damage by dedicated DPS builds such as EleWarlock. For what it does–CC + reliable and consistent damage–the build does it well.
Inevitably, though, since you’re still at R8 (I believe?) you should expect your damage to be somewhat subpar. The ultimate test of whether a Wizard would perform properly would be whether you are well-geared or no and that usually comes about after you’ve spent some time at max level chasing optimal gear (and I’ve certainly been there).