I have beat all the Rulers by Shadow Ops classes in legend before. Here is my tactics.
Combat Engineer using Fastball to launch Frost Grenade first. You got 2 action before Rulers could react. The Archon King will react after 1 Xcom action. The second action is remove armor. Launch a grenade or a Keen Edge Hunter using Slice&Dice to do this role. The third action is remove armor again if you can`t clear up yet. Now, the Rulers could react. We could just push the end turn button when there is not the other enemy in mission.

In second trun, shoot a Frost Grenade again if we have Pack Master(GTS unlock). We got 2 more action. Lets do as much damage as we could. First, using all free action attack, such as throw Hunter's Axe or Lightning Hands from Sharpshooter. Fastball and Slam Fire is not a free action attack. Don`t count them. The most DPS perk is Full Auto from Infantry. The second is Bullseye from Hunter. You could also use the Bolt Caster in the second action for stun the Rulers. Bolt Caster has 50% chance to stun for 2 more action. After 2 action from frost, the Rulers should escape or return fire on your third action. All the control tools are gone, all you could do is just shoot him in the cover.

End turn could make your actioned soldiers ready for next turn. Such as your Frost Grenade or DPS soldiers. Stasis Field from Dragoon is a perk that could freeze the Rulers to earn the chance for solders to reposition for next turn.