Suggestion: Either limit the sticky jumper to one sticky out at a time (still allows air pogo) or tell people that "Hey, if there's a demoman flying at your face, you should probably stop sitting in spawn and start running away." On nearly every map that's not indoors, a demo can 2-sticky right to the red spawn and pick up kills on a good portion of the red team before any pyros, and in some situations, even soldiers, can get there. I don't think it's a fault with the sticky jumper so much as a fault that new players all love to hide right in red spawn and don't know to run from anything besides pyros, but until there's some form of tutorial - I'm not even sure how this would be implemented, if at all - it's the only fix I can think of.
Also, I'm not sure if this is even possible, but is there a way to (easily) un lag-compensate weapons that kill in one hit? I've got no problem with being hit by an axetinguisher or something similar but when it appears that they missed by 15-20 feet to everyone but the guy with the weapon, it becomes a little bit frustrating. List of weapons like this: axetinguisher, postal pummeler, market gardener, ullapool caber (this one's especially frustrating because there's no prerequisite to hitting you with it like the others), and any demoman melee weapon during a charge n' targe or splendid screen charge.