Relax pal. I posted my opinion after you posted yours (without any reasons).
There are more than a few tournament players out there that feel that Lizards are the top army with skaven in second place. Please list the armies that you think are ahead of lizards if you would place them in the middle tier. I honestly can't justify placing the lizards any where near the middle.
It's really impossible to accurately decide this due to the different meta that everyone faces. Skaven may be number one in your area but something else could be the top in my area.
Screaming bell, dreaded 13th spell, slaves (2 pt exploding ld10 infantry), HPA, WLC, Warpstone tokens, doom rocket, brass orb are all filthy and they have lots of other choices that aren't as filthy but are still great
Doom Rocket and slaves are broken, I totally agree.
13th is bad but it is tough to pull off and only targets infantry.
Brass Orb is great but not game breaking in my opinion.
HPA is way too cheap but it can be dealt with.
WLC is a too few points but not that bad. There are many games where it does nothing due to the randomness of it's rules. I would much rather have a dwarf cannon with a few runes on it.
Warpstone tokens are fine. I have never heard these mentioned as broken.
Screaming Bell is a great option for a Grey Seer but cannons are a big issue. I have had my Seer shot off the Bell more than once in the first couple turns of a game.
Skaven are a very powerful army, no doubt, but I'm not convinced that they are clearly number one.