Good discussion of the Kickoff Table. Now let me tell you where I think you're wrong
A few results that you saw as neutral, I see as favoring the offense (if only slightly).
Changing Weather: 3 of the 4 bad weather results impact ball-handling and therefore favor the defense, but the more likely results favor the offense: if you happen to already have bad weather, Changing Weather will tend to remove it; and if you had nice weather, the extra scatter increases the chance of a touchback, which also favors the offense.
Pitch Invasion: if the number of stunned players on each side is relatively even, then this result generally favors the offense. Not only do they get to react first to the new board position, and stand their players up first, but they have fewer tackle zones to deal with, which can be huge. (Corollary: being short-handed is generally worse for defense than it is for offense -- which also makes Sweltering Heat slightly better for offense.)
Also, I think you're setting up false dichotomies by judging Blitz directly against High Kick (and Perfect Defense against Quick Snap). The probabilities of both the offense-friendly results are higher (11.1% each) than those of the defense-friendly ones (8.3% each). Add in Changing Weather and Pitch Invasion, and the table as a whole favors the offense; so to my mind, it's right that the defense-friendly results have more punch.
Personally, I just think the Blitz! result is fun. Suffering the Blitz is a rite of passage for every Blood Bowl coach, and learning to set up your offense in anticipation of one is a mark of maturity. Having said that, I agree that they break individual tournament games*. Underworld Cup this past weekend had a nice tweak, where only 3 players (not in TZs) could get actions on a Blitz. But I think limiting to 1 player is okay, too (think Troy Polamalu diving over the line).
(I had one tournament ruined by Wood Elves getting 3 consecutive Blitzes against me --
and he had a hypno-gazer. Try protecting the ball against
that. It was fun to watch though!)