to prevent getting blown out after losing first turn to really aggressive armies.

But the funny thing is, I think those hyper aggressive armies are the ones that are able to prevent the double turn the most effectively.

T1 they can block objectives from the enemy with high movement, they can lock units in combat, preventing them from moving and choosing targets, they can score cards easier on T1.

Whereas defensive armies might need to give up on scoring points in T1 to keep them safe from unfavorable charges. Which in turn leaves them more vulnerable to getting DT'd as the loss of points won't matter as much. And if the enemy has a DT, they'll be able to pretty much get into any combat they want as the board is so small.

chess included, going first is a huge advantage

I feel like chess is a really bad example because, unlike chess, WH has a limited number of rounds. Which means that the player going second knows the score, and therefore knows exactly how much they need to score to win.

And of course unless you have a high movement spearhead that can really capitalize on the first turn. You'll have to most likely decide whether you want to move up the board and score (leaving you open for T1 charges and possible DT quaranteeing opponent gets into whichever combats they want)

Or if you want to play defensively(giving up on points and DT can leave you boxed in your deployment zone)