I've sunk 2000 hours into league and probably less than 100 hours into hots and i have more of the hots content than i do of the league content in terms of percentage. League has a lot more stuff in it though.
I've only played the game so much, and my view on the right way to play the game shifts every now and then, but I think the team leveling is somewhat of a double edged sword. If you farm experience, essentially ignoring objectives as much as possible while staying near every minion wave until you're two levels up on the opponents, it becomes very hard for them to win a teamfight against you and puts you in a position to snowball for a long time. Hitting 10 when the opponents are still 9 also gives a good opportunity to easily win a fight, pushing you to level 11 and starting the snowball earlier.
There isn't a lot the team that is behind 2 levels can do except defend as well as they can until both teams are level 20+ and the level gap becomes a little less relevant. That's still a better outcome then in a lot of mobas though, which offer no realistic chance of comeback or offer inconsistent chances for comeback that aren't reliant on the behind team's ability to play but more on the ahead team making mistakes. Most games of HotS do reach level 20, so teams always even off by the end-game.
Blizzard's putting in a matchmaking change soon that makes it so teams without a healer won't ever queue into teams with a healer. Lili is my favourite healer for pubs because she can pull off a lot of damage if your team doesn't seem to provide enough and a lot of healing if your team has a competent carry.
Lili is pretty awesome. The fact that she can kick someone's tail while being a cute little panda kid is just icing on the cake.
I agree with about everything you said. Granted HOTS is new while LOL is very entrenched means of course it'll have more content. HOTS will likely grow this way as well as long as it can get a dedicated community in the way that LOL did.
The hot button issue for me is the community. I'm okay with losing a fair fight. The last game I ever did in LoL was in the first five minutes of the game. Someone decided they were going to be team captain and started telling everyone what to do. Someone else on the team decided they didn't want to do that and starting yelling at him. Insert long round of racist and sexist commentary followed by self appointed captain running straight into the opposite team to feed them xp for the rest of the match.
Sadly as bad as this was it was simply the last straw. MOBA's are a lot of fun but they tend to draw an utterly toxic community. I give RIOT a lot of credit for trying to clean this up and I really am rooting for them. But I can't help but wonder if the nature of the game itself draws these kinds of people.