You have a few options depending on your playstyle. Scrap of the Soul Cloak if you use a supercharge. Eye of the Gemini if you use a supercharge and you like its synergy with the Soul Cloak. And either Tetra, Omega, Solar, or really any other one that you like. Solar seems to be the go to for just the might buff alone. But with new artifacts coming with the next DLC, we might can expect another Artifact that might be worth using.
Soul cloak Eye of Gemini Solar amplifier ———————— If you want to be more of a team player Soul cloak Tetra Eye of Gemini
Soul cloak Eye of Gemini Solar amplifier This is the current dps meta. Hold off though. In a few weeks, there will be a few new ones that might, or might not, be better. The solor one is better for not only the might buff, but also for using heat vision for single target loadouts. You probably see plenty of people with blue heat vision.
Can Tanks use any artifact, like a healer artifact? If so do tanks get bonuses that a healer would get out of them.....
Orb of Arion requires a power with the keyword Priority Heal. Only healer power sets have that kind of power.
As a Fire Tank you may be interested in Dilustel refractor, for increasing your health, Mistc Simbol of the Seven, which increases your defense, your restoration and dominance, and your incoming healing, and Manacles of Force, which lowers shields cooldowns, increases restoration and dominance, and has a proc that absorbes a high% of an attack that would damage you for a %of your life (can't remember exact numbers right now). Those are some of the best tank artifacts but you can take a look at others like Eye of Gemini or Lazarus Pit Water (mainly at max rank, which is hard to obtain and won't be available until this Thursday).
I use the Soul Cloak with Gemeni and Dead Kings Scepter. You could use the Solar Amplifier, but Heat Vision doesnt hold my interests, and Im happy with my current setup. You can also top the charts, but you have to know how to use your power. Just my personal preference.
I have both currently at 160. Didnt bother wasting catalysts and money to get to 200 day one. But the Dead Kings Sceptor seems more of a interest to me than Glimorium. I feel I could squeeze out more numbers with how my rotation is set up, and also how much it procs. Ill do some parsing when I get home from work and see which one outweights the other.