God Tier

-Laser
-Nuke
-Infantry
-Salvage

Good Tier

-Superweapon
-GLA
-Demolition
-Special Weapons
-Armor

Decent Tier

-USA
-China
-Tank
-Toxin

Kind Of Bad Tier

-Airforce

Prince Kassad Tier

-Stealth

Using your own ranking:

Excellent

-Special Weapons
-Laser
-vChina
-Salvage
-vGLA (Scuds and triple Marauders are seriously good, Balloons are comical, especially when you manage to defeat someone with them)

Good

-Demolitions
-Infantry
-Airforce
-vUSA (Pathfinder/Marine Exos and Avengers are all you need)
-Armour
-Nuke

Poor

-Toxin (without Virals he cannot do anything)
-Superweapons (too boring and bland to play as)
-Stealth (cannot do anything late game)
-Tank (nerfed harshly to the point he can't really do anything and is now confined to a support role)

edit: I wouldn't say AFG is 'bad' (Stealth Commanche spam are super annoying) but I find he is rather boring to play as.

Great:
Demolition
Laser
Nuke
Salvage
Special
SW
vChina

Ok:
Armor
Infantry
vGLA
vUSA

Meh:
Airfarce (Airforce)
Allergies (Toxin)
Hiding (Stealth)
Junk (Tank)

I'm just going to focus on the bad teams, and my reasons and observations why.

Stealth: While certain factions he excels at defeating (Air, Infantry, etc.), others (Tank, Armor, any faction with more-than-paper armor) he struggles at due to a lack of decent anti-tank weaponry. He survives only because he has many near game-breaking tactics (Barracks Tier Hijackers, overpowered salvaged sniper quads, etc), but he dies late-game if the player does not exploit these tactics.

Toxin: Same as above. He excels at murdering air and infantry generals, but he struggles against tanks. His Virals and Nerve Gases are good, but one requires a late-game upgrade and Nerve Gas is difficult to use. What made him good in ZH (Anthrax Gamma) was (Rightfully) nerfed.

Tank: While in paper this General is decent due to his Focus on Tank-Spam, in practice this general is terrible. V-China without the BM upgrades out-produces him in tanks. With the BM upgrades the Tank General has no chance. The things that made him good in .951 were (over-)nerfed, and this General has pretty much fallen from his once-high position. My patch attempted to find a happy medium, which worked somewhat, but he still needed some tweaking.

Airforce: Actually there is one game-breaking tactic that wins nearly all games. Acolyte Drone spam is both cheap and quick, and works in nearly all games. No general can produce enough anti-air fast enough to break this tactic. Other than this though, this General is weak due to his difficulty with defeating swarms. Tornado Bombers on paper would take care of this, but they are quite weak in the current version.