If you're group isn't seeing the issues where the person who gets first turn normally cripples the other, you are one lucky man!
We have a different definition on what an "Alpha Strike" is. To me, it's a term used in Warmahordes when the guy pops his feat, and then the game ends; he either kills your caster or puts himself in a spot where he will get killed next turn himself. Either way, game over, and all this "Page 5, play like you got a pair" bullshit is right out the window as everyone timidly moves their models about the board setting up for the perfect Alpha Strike; it's why I gave up on Warmahordes a long time ago. In general terms, it's when a model/unit uses it's BIG/ONE TIME ability to end a game.
The biggest issue I see with 40K 8th is vehicles. If you have nothing but infantry and the other guy has a good mix of vehicles and infantry, you are going to get shot off the board pretty quickly. I have a buddy who runs IG and has about 10 Chimeras, each with heavy bolter/multilas/heavy stubber. Combined with first-rank-fire, second-rank-fire, barley anything gets across the board, and that which does can easily chew up guardsmen, but take forever to kill even one Chimera. We're talking roughly 100 wounds at T7 with a 3+ save. Brutal.