While I agree that there is little class definition between THM and CON, I don't think the answer is to make them more alike (via giving them the same AoE type)
The Radial AoE allows you to knock out selected groups of enemies, whereas THM would aggro pretty much everything in view.
As for nuking, good luck. If you're fighting near your own level(up to 10-15 over your CON rank), you can shell out some pretty nice damage if you know your elemental wheel.
That being said, On NM's above your level (Uraeus, Dodore, Bloatbelly, Buffalo, etc) nuking is nearly a waste of your MP. The great level difference turns your nukes into little more than scratches. With INT and PIE having a tiny effect on your spells, cons go to NMs pretty much just to heal and buff. If you want to be (damage) useful in an NM fight as a magey~type, use DoT's.
If you want to be a BLM, it all boils down to magical accuracy. You can have potency oozing out of your rectal orifice, but its all for nothing if it gets resisted.
FFXIV: Taiga Halak, Fabul
FFXI: Talina, Valefor (retired)