[Linggango] Progression tips for Terramity?

I've been playing a lot of Linggango recently and having fun but I've been finding myself very gated on the damage end. I feel like every boss has so much HP for no reason and the balancing is odd, but the real problem I've been having is with the spire guardian...

Most other bosses I've run into can't quite kill me so casually with my enchanted voiderite armor, but the guardian just oneshots me. With how little damage I deal (current weps being the super big great sword and voidfang saber) dodging until I kill it is out of the question as well.

I'm already far into the main progression line (bringer of doom), so I'm a bit baffled by the fact that I'm already at my limit at the terramity boss that unlocks the second tier of stuff, let alone the rest. The weapon tierlist in the quests section seems a bit lackluster and inconsistent. Perhaps spells with ars and iron are much stronger, but I much prefer playing like a barbarian and hitting stuff with my weapons, and the spell mods are too confusing for my smooth brain anyway.

How did other linggango players here get through the guardian? I don't feel as though I can fully trust the tierlist, what weapons should I have/be aiming for at this point in the pack? Any general progression tips?