I was reading wikipedia about pyromaniac perk. Do we still need explosives skill to get that perk? Since it doesnt affect any explosive weapons except Grenade launchers incendiary grenades ( and fire bomb). Is it really meant to be like this? If yes then can we get it to affect most of the explosive weapons? Or change the requirements to Energy weapons ( flamer , incinerator, etc etc).

It was meant to be explosives. It was that skill in fallout 3 and remained so in fallout NV. Every weapon class has a fire based weapon. It doesn't give some minor damage boost. Its 50% accept the fact it requires an investment not an automatic requirement from using one of the weapon types that benefits from it.

It effects the melee weapon shiskebab, but it doesn't require melee skill, it effects the superheated saturnite fist but doesn't require unarmed, it effects flamers and incinerators but doesn't require energy weapons. Honestly if anything when I think of being skilled with handling fire explosives sounds the most logical choice due to the dangerous and unpredictable nature of fire.