How do these weapons fair, when it comes to PvP or PvE normal NPCs?
Depends.
AX Missiles are alright.
AX Multicannons are alright.
Remote Flak is fun to shoot at things with, but generally useless against NPC's or other players.
And that's how they were designed to be - strong against aliens, weak against humans.
As for all this "But, I have to go over here, to get something to use over there?" business...
I have a fully AX-Outfitted Type-10 parked somewhere in the neighborhood. Since I spend less than 1% of my time shooting at artichokes, I'm perfectly happy to have the tools on hand where they're most needed. It's called Planning. I planned for engaging Thargoids when necessary, thus have what I need near by. No long waiting or playing something else while I wait - just jump out to the area, change ships and I'm ready to go.
And yes, it has C3 AX weapons on it. From Way Over Here, hauled all the Way Over There, so it's ready to go when I am.
A lack of planing on anyone's part does not constitute a design flaw on anyone else's part.