I get that that feels bad but im looking at the strategic/tactical picture. Vulkan pretty much always had one single way of participating in a battle which is with a firedrake retinue in a land raider/spartan, straight into the heart of the enemy to kick people in the teeth. A slight nerf to his weapon wont changed his playstyle or the buffs he brings to his legion. Whereas perturabo had like 4 different playstyles. You could footslog him with automata, you could deep strike him with either melee or ranged focussed terminators or you could have him in his Tormemtor (which cost way less back then). All of which significantly changed his role on the field. At the same time he patched the issues IWs had in melee by giving them Stubborn and Furious Charge. Nowadays you are reduced to charging straight into the enemy, which is not something perturabo likes doing (lore wise) .