Are you up for tackling the double Diablos hunt? Once we're done with that, we can fight Deviljho.
Also, wearing the Vangis armour I've been clobbered enough to know that Deviljho is equally weak to both Thunder and Dragon, so use whichever weapon you have with the higher element.
I checked the wiki and the Long Sword has a para LS but it only is avalable to awaking users. Don't have Laggi armor yet but I'm thinking Laggi armor would work better with the elemental Long swords.
It isn't worth it unless you can gem in Awaken. The Lagiacrus armour has Status Attack Down, and although you could cancel it out easily enough, with the available slots there's no way to make it become Status Attack Up.
Plus I've noticed that switch-axes seem to lose their sharpness faster than great swords.
Technically they don't, but it feels that way. Weapons lose sharpness after a certain amount of hits, so the quicker weapons that attack more often will need sharpening sooner. This is why the knife will lose its sharpness quickly and the great sword and hammer will take a while.