It must be done because they make no sense and it shows how little effort they put during this expansion with the rogue class.
Look at Mages :
Tier 1 : About moving when casting.
Tier 2 : Survival.
Tier 3 : Freezing Control.
Tier 4 : Thematical Survival.
Tier 5 : AoE
Tier 6: Damage/Mana
It's all clear and clean.
Now look at ours :
Tier 1 : Stealth (Good one, it's how it should be)
Tier 2 : Two old skills as talents to reduce enemy damage plus...Deadly Throw? What is it doing here?
Tier 3 : Survival(?) consisting in a poison (poisons should have own tier) and a spammable 30% damage reduction over Feint.
Tier 4 : Some kind of an attempt to a mobility tier which consisted on stripping the subtlety spec of its grandeur in order to make all three specs equally immobile.
Tier 5 : Control tier. Not so bad, but again a poison here which means that we're the only class, as far I know, that can negate a talent by picking another. Warlocks got a fix in regards to this.
Tier 6 : Rule breaker (?). All this should be baseline somehow.
It's way too random.
I'd suggest something like :
Tier 1 : Stealth.
Tier 2 : Mobility.
Tier 3 : Poisons.
Tier 4 : Control.
Tier 5 : Survivability.
Tier 6 : Flavour cool stuff.