I've been gone a long time.

Looking at http://www.swtor.com/info/eldergame, it says that Artifact gear is supposed to have a set bonus.

I just completed those missions and have my suite. e.g. TH-31A Elite War Medic Helmet.

I tried it on and no set bonus.

Am I missing something?

Wow, yeah, that guide is outdated. One, level 53 [Artifact] gear never had a set bonus. Two, the gearing scale has been reworked since that guide was made.

Level 53 Artifact gear is no longer purchased with comms, but drops from the CZ-198 weekly mission and the Oricon story quests.

Basic comms are used to purchase Black Market gear, which also drops randomly from bosses in 55 HM Flashpoints and 55 SM Operations.

Arkanian gear is the same item rating as Black Market, but has a set bonus. Tokens redeemable for Arkanian gear drop from bosses in 55 SM Operations, with each boss always dropping a particular token.

Elite comms are used to purchase Verpine gear, which also drops randomly from bosses in HM Terror From Beyond and Scum & Villainy, and also from the last two bosses of SM Dread Fortress and Dread Palace.

Underworld gear is the same item rating as Verpine, but has a set bonus. Tokens redeemable for Underworld gear drop from bosses in HM Terror From Beyond and Scum & Villainy, and also randomly from the last two bosses of SM Dread Fortress and Dread Palace. As with Arkanian gear, most bosses will always drop a particular token.

Ultimate comms are used to purchase Oriconian gear, which also drops randomly from bosses in HM Dread Fortress and Dread Palace.

Dread Forged gear is the same item rating as Oriconian, but has a set bonus. Tokens redeemable for Underworld gear drop from bosses in HM Dread Fortress and Dread Palace.

For more detailed information, read Dulfy's gearing guide and loot table.