Artifact, no question. You can fill slots with full BoE's if you choose. If you want to remain full Plate you won't even hit the iLvL a 101 can with mixed Gear and since there's Int Gear for every slot, why not. Granted I don't recommend mixed gear for non-Main Stat like a Warrior wearing Cloth Shoulders as example. If you are curious about Gear choices check my Sig for my 101 Shockadin Haggas.
Outside of Boe's, you should be running TW day/night when it's up because you get access to ~815 iLvL (same with Event Holidays) so at the very least you can fully Gear out your 109 through TW, Crafting, Legion Rares and Violet Hold and end up somewhere around ~805 iLvL (full Plate). That'll give you a good starting point to then slowly purchase the BoE's you're happy with.
Some points about Shockadin (unf "Healers" don't work in Raidbots so I still haven't been able to DPS Sim mine for proper Stats):
- Crit: 50% is the hard cap sub 110 for Holy Shock, anything more is of far less value.
- Mastery: useless unless you're building it as a Healer 1st, Shockadin 2nd (but you're going to get tons anyway).
- Haste: 50% exactly is 1 sec GCD.
- Versa: This is what I stack on mine since I'm already over 50% Crit/Haste and there's nothing I can do about it.
- Relics: 810's if you can get them, otherwise use double Holy Shock.
- Leech: meh, it's nice to have but frankly Shockadin is beyond God Mode (at least in PvE).
- SOCKETS: Dooo eeet!