the Alt-P gear is balanced differently, so yeah the items do not appear as powerful - specially melee weapons dmg ratios, but the difficulty of mobs is also tuned accordingly.
When you passing through Crushbone (which a tiny zone packed with 30 levels worth of mobs), you taking on yellow/red con mobs, sometimes 2-3 at a time, and you need the buffed up gear to survive. But that's not the case in the Alt-P.
By using Donator weapon, you effectively killing the entire challenge of doing the Alt-P in the first place, cause mobs nowhere as tough as those in the main progression.
And of course, if you plan to participate in upcoming Contest, the donator weapons won't be allowed, as we expect a fair competition for everyone
