So far there have been a bunch of discussions on this.
Who thinks what armies belong in what tiers.
I think that the top armies are as follows.
Daemons of Chaos
Orcs (possibly but rumors of new army book coming soon)
All the other armies don't matter I am just listing what I think top tier armies are.
I think all the others basically fall into the same category.
Here are my reasons summed up as quick as I can for each army.
Core units are crazy good. Basically like having an Undead army that is way better at everything.
Flammeres and Flesh hounds enough about those units.
Special Characters Break the game, Karios, Mask.
Their Magic Banners, -2 LD, and Stubborn banners are crazy good.
ASF for everything!!!
Teclis (need I say more)
Spearmen are super legit, archers not to shabby.
Phonix Guard Almost Impossible to Kill.
White Lions Nasty.
Also, BSB that makes a unit Immune to magic wow!!!
Ability to always have more dispel dice then you have power dice with Arch Lectors and Priests. Really Really good.
Can take any of the lores of magic and abuse them easily, by taking cheap wizards.
Engineers within 3 inchs of machine reroll artillery. Almost makes a dwarf engineer obsolete.
Steam Tanks, Morters, Great Cannons, Helbasters, and Hellstorms!!!
Not to mention big blocks of Flaggelents and Halberds are not bad.
Thorak (everyone knows why hes good)
War machines that are magical and flaming WTF?
Bolt throwers for cheap and lots of them yikes! Surprised I did not see the 12 bolt thrower 6 cannon list at ard boys.
T4 and better for the whole army good stuff, great armor, good fighting ability.
Crazy good banner combo's and best of all their ability to dispel everything they want.
Finally the Orcs:
Ability to take lots and lots of warmachines that are actually great, and still have tons of room for troops that hit hard, and so much crazy good magic.
at 2500 points you can take 6 bolt thowers 3 rock lobbers, 2 doom divers, 4 snotling pump wagons, and still take another 4 chariots.
And that is not even half of the points to spend on your army. Wow.
Also their miscast table is not bad, so risking a dude every turn on rolling 6 dice does not matter.
Also 35 and 65 point casters is crazy stupid because you can get all the spells you need and when you want to blow up a guy to change the game and get a crazy good spell off you don't care.
Finally the dispel dice banner. That is great. Getting all those extra dispel dice pretty much keeps your army safe from magic.
So there you guys have it. Those are my pics.
There are lots more reasons for each army being in the tier they are in.
But I wanted to keep it kindof short. Even though its still pretty long.