>>23381782QD volc is super bad this generation. Talonflame basically invalidates it entirely. Even 252spa/252spe 3 attack variations are utterly dependent on nailing it with hp rock on the switch. It's basically scarf terrakion turned up to an 11 in terms of its ability to kill volc.
Yes you can obviously just remove it, and Volc has several unique qualities like a resistance to bullet punch, mach punch, and ice shard coupled with flame body. But it's a super poor fit for HO this gen.
I know people will just say "so just remove talonflame before you set up" but even with Talonflame gone you still face plenty of problems from Ttar, Heatran, newly buffed defensive juggernauts like Chansey, etc.
You can still totally run Volc it's viable, but it's just so inefficient when you can have pokemon with similar reward for less maintainence and risk involved. Lack of perma sun is also a severe nerf to it.