I had more combat tricks in the past, too, but they weren't cutting the mustard. Vines of Vastwood was barely playable, but just as often sat quietly in sideboards. I liked the idea of Briarhorn, but didn't bring it in cause I knew it couldn't compete. Agony Warp caused tons of blowouts here, too, but it was the removal aspect that people were taking it for.
All that's to say that I agree with your hypothesis - combat tricks can't thrive in a typical high-power cube.
My take on it is this. For combat tricks to do their duty, high quality, universal removal has to be toned down. It's hard to justify jamming a Giant Growth if you put your opponent on Path to Exile, Lightning Bolt, Terminate, or one of the myriad other cheap removal spells. The chance of getting eaten alive during combat is just too high. Good sorcery speed removal - your O Rings, Wraths, Flametongues - also contributes to the problem. If you know that creature attrition is high in the cube metagame, you want to increase your deck's creature density, and decrease the number of spells that rely on creatures sticking.
RTR limited is a great example of a combat trick laden environment done well. Selesnya alone had something like six combat tricks in the mix. At the same time, most of the set's removal was conditional, or expensive. Your gold creatures are immune to Ultimate Price; your opponent needs 6 open mana for Explosive Impact; their empty board means they can't cast Launch Party. And so on.
Toning down removal in a cube environment has a cascading effect. If removal is now going to miss half the creatures, or require some finesse to set up, creatures in turn need to be dialed back. Otherwise, the likes of Hero of Bladehold or Wolfir Silverheart will end every game on the spot. To say nothing of the game-dominating Titans, which cubes are having trouble containing even now.
If creatures are weakened, spells might also need to take a hit to fall in line. I don't know. I don't want to think about it any more.
Anyways. This is why I'm so eager to see Kevin's cube. :)