The Tarkrip are the worst of them, though their named means Dunadan-Ripper (Tark= Man of Gondor or Dunadan of the North) And I dont think I've ever seen a Tarkrip Uruk. Also they're like the Exhiles because you see them in North Bree Fields and Separated from the Ongburz and Blogmal in the North Downs, and also separated from other Orcs as they are in the Lone-Lands. Tarkrips are usually Swarm to Elite Master a few are Nemesis.
The Krahjarn are mostly Uruks, they are also the strongest and Best of all Orcs in the game, they're usually Elites all the way up to Arch-Nemesis (The Krahjarn Iron-Defender located in the Ettenmoors for instance)
The Blogmal are both Uruks and Orcs in even numbers (meaning the Uruks are just as Usual as orcs in the Blogmal) Of all the Orc tribes the Blogmal seem the most Primitive (apart from goblins and orcs of moria) and they also serve as the Orcs who defend places claimed by the enemy, as the Krahjarn are the Elite Guards of Locations directly made by the enemy. Blogmal range from Normal to Nemesis.
The Ongburz are the shock infantry of angmar. They are the toughest ORCS (not Uruks, Krahjarn Orcs are usually normals and Sigs) they serve as the forefront of Angmar's Assault upon eriador, they are rarely seen defending, I've almost always seen them attacking places... They Range from Signature to Nemesis.
The White-Hand orcs are as named, they are the Orcs of Saruman, also some are the Defective Blogmal and Tarkrip. They are usually not formidable foes, and are usually found at they're camps in the the Lone-Lands, nearly all throughout Dunland, and ALL over the place near Isengard. There is also an Ambassador force of 'em located near Barad Gularan. They range from Normal to Elite Master...
The Uruk-Hai (Uruk= Orcs (Orcs in mordor are referred to as
"Snaga" or slave) And Hai ,means "Folk" so they are the "Orc-Folk") are the Uruks of Isengard, They range from Normal to Arch-Nemesis ;D
The Shak-Hai (Shakthasi means craft, Shakalog Means distil, Shakab means Eagle, and Hai means "Folk" or "People", so they Good be the "Craft-Folk" or the "Eagle-Folk" or even the "Distil-Folk" which could mean they are ones who make poison but I find that one unlikely. The Craft folk makes the most Sense to me because Saruman was known as Curunir before his downfall which means man of Skill... but then again, as Tolkien stated "The Orcs can't make anything other than Mockeries of what the Free Peoples make" So... Well, those are all the Orc tribes I can do my best to explain for now.
"The Grey-Company were the bravest, and the Best mortal soldiers in Middle-Earth, Excellent with spear and bow and sword."