We are in agreement that they would have pushed both guys, but seeing as how he did become a bigger star than Lesnar ever was, I don't see why he still wouldn't have become the bigger star even if Lesnar had stayed.
Because he became the bigger star because he was able to be given the space that Lesnar vacated, and ended up becoming more popular in that spot. If Lesnar hadn't left, the spot wouldn't be there for Batista to fill, and he wouldn't have been given the oppurtunity to become the bigger star.
This is where I really disagree with you. Why wouldn't they have pushed Batista the way they did? Lesnar was supposed to become a big time face, but he basically flopped. It's obvious that they wanted to him to become an uber popular baby face with what they had him do at WM19, but he didn't get over well enough as a face. So they still would have had that big time face void to fill, and Batista would have still been one of the guys along with Cena to fill that void.
Batista would've still been looked up to fill that void, you're right, but he wouldn't have been looked to to fill it at the top level, as one of the big 3 guys. He would've been looked to to fill the void of a main event face, after the recent losses, which is why we both agree he still would've been pushed, but I don't think they would've needed him to fill the void of being one of the top 3 or 5 guys. If Lesnar stayed, they would've had enough star power at the very top to be comfortable with it, and wouldn't need to make anothe rmega-star, whether face or heel. Lesnar left, so they then had a huge hole to fill, and had to make Batista one of the top guys, as in book him to have a Hall of Fame type career. If he hadn't left, the void to fill wouldn't have been as big, therefore he only would've had to fill a smaller spot, thus making him a true main eventer, but not the type of future HOF'er he's on track to be today.
This is the best example I can give...
If Lesnar stayed, today would've been something like..:
Tier 1 : Cena, Orton, Lesnar, Triple H
Tier 2: Shawn Michaels, Batista, Chris Jericho, Edge, Rey Mysterio
There simply wouldn't have been the need to make him the megastar, and face of this era, because Lesnar would've already had a headstart there.
Now that he left though, the hole to fill was bigger, so they, instead of pushing him to be just a main eventer, pushed him to be a megastar, and face of the era...