I think the "tier" the TS meant are tiers in talents, not tier in armor. e.g. and I think WoW only has up to Tier 4 armour now right? Correct if wrong.

For the Affliction tree
Tier 1 talents = Suppression and Improved Corruption
Tier 5 = Shadow Embrace, Siphon Life, and Curse of Exhaustion
Tier 9 = Unstable Affliction

For Demonology Tree
Tier 1 = Improved Healthstone, Improved Imp, and Demonic Embrace
Tier 5 = Improved enslave demon, Demonic Sacrifice, Master Conjuror
Tier 9 = Summon Felguard

Please refer to http://www.worldofwarcraft.com/info/classe...ck/talents.html

Hope this makes it clearer for you. For now, the deepest talent that you can get are Tier 9 talents.

You can make your Corruption spell instant once you have put 5 talent points into Improved Corruption talent. IMO, this would be the first thing that I put when I play warlock. But just my RM0.02 la. Have fun!