I've personally never had a problem playing against Tyranitar, but that's probably just me. I don't really have an opinion about where it should be though, but I'd probably say it should be banned.
On one hand, it has great defenses and HP (all above 100) and an amazing 134 base attack. It's pretty slow, but 61 is just enough to outspeed anything that's not trying to use alot of Spd EVs (Everything below 60 usually doesn't use any, and often a -Spd nature). It has a good movepool too with EQ, Crunch, Dragon Dance, Stone Edge, etc.
On the other hand, it has extremely common weaknesses in Fighting, Ground, Water, and Grass. The person using Tyranitar can easily predict when these are coming though and simply switch out. The weaknesses alone are not enough to keep him in OU if he deserves to be banned from it.
As for Manaphy, it's been said already, but Rest is not the problem against it.