I think this is an interesting story for those of you interested in the game design part of things. A top C&C 3 and Kane's Wrath player, Apollo, posted a short piece on the GameReplays.org forums
about the role of "luck" in C&C 3. He says, essentially, that there are too many parts of C&C 3 that are beyond a player's control for the game to be a true matchup of skill.
There are far too many "luck" moves and incidents in the game that drop the skill level, things like the unit AI, engineers, scouting and most of all balance. How easy is it too snipe a top 10rank player? Drastically easy. You can snipe them even if you are rank 5000 on the ladder because of the list above.
I think he makes a fair point. Certainly, C&C 3 has many flaws in this regard, and he points out a few of them. Engineer micromanagement is notoriously luck-based. Buzzers are even worse (good luck predicating who will win a Buzzer battle regardless of the micromanagement of the two players). Pathfinding can be bad at times as well, and units often make mistakes when they're on their own. So, certainly, these parts of C&C 3 and Kane's Wrath can have a particularly high impact on the game and should be corrected. Anything else is poor development.
But I'm not sure that these alone are the parts of game design that accounts for much of the volatility online. First, remember that some volatility is a good thing. Second, the broader problem is that too many of the tactics are too tightly-drawn and can only be countered with prior knowledge, yet spending time and resources scouting isn't sufficiently rewarded because of the propensity for unit spam. Build orders that involve off-beat tactics like Shadow Team rushes are deadly unless one's opponent knows that they are coming--and if he knows that they are coming because he spent his early game scouting and exploring, he's open to the typical C&C 3 storm of Black Hand units. Basically, there are problems in C&C 3 and Kane's Wrath that create too much randomness in games, but it's not merely limited to the glitches in the game, though those are present as well.
This might raise some interesting questions for those who play online, who seek to mod games, or who are interested in the game theory present in C&C.