Actually, Shroomite was the easiest post-Plantera armor set to obtain because all of it's materials can be easily farmed (It's real problem is that the helmets don't even boost all ranged weapons and it only has one set bonus, which is something I don't understand why it wasn't changwed in 1.3 even through almost nobody liked that)., while the Piranha Gun's real strenght is that it has a constant DPS and allows focusing on dodging (And that it wastes Diabolists and Necromancers, but that is more situational).
The real problem with Vortex Armor is that it's set bonus is almost identical to Shroomite's. There is also that the Vortex Beater seems to be rather lame (I say "seems" because I can't actually play due to a random crashing bug), specially as none of it's weapons do anything really unique (The Vortex Beater, for example, could have been a weapon that can act as the Chain Gun, a shotgun, atc... rather than simply having homing explosives).
The real problem with Vortex Armor is that it's set bonus is almost identical to Shroomite's. There is also that the Vortex Beater seems to be rather lame (I say "seems" because I can't actually play due to a random crashing bug), specially as none of it's weapons do anything really unique (The Vortex Beater, for example, could have been a weapon that can act as the Chain Gun, a shotgun, atc... rather than simply having homing explosives).