valiantI don't think this was a nerf because of parachute. If it was, they would have nerfed damage directly or they would have prevented Demo from being able to use it. This was a calculated decision.
Neither the 6v6 community nor Valve was going to change their views on how they think the game should be played. Valve wants to see meta shifts and usage of the different classes more often, while the 6v6 community dislikes this because the other classes and weapons can be dumb, bad, or unbalanced.
This is Valve's way of reaching out to us.
snipped the majority of your post, but i don't know why you think Valve considered the competitive community at all in these decisions. from what i can tell (and there might be a quote or two on this), they have openly supported and agree with the Highlander game system, as it mimics something of an organized pub with a lot more unlocks than sixes.
the sticky nerf might even effect HL more than 6's with 450 heavies and wrangled level 3's (not to forget that minis take 2 stickies to destroy, as well).
just as you speculate that the damage nerf was related to imploring the community and the meta to change, i speculate that it was directly related to the base jumper.