I wasn't going to write a solution for this... but.....
I found this method was faster than the other solutions and far less stressful.
Use these settings:
Any map
Strongholds
+10 pop per Stronghold point
No Fog of War
Any helpful skulls, in particular Emperor Skull for the cooldown reduction. Although, I'm not sure how much it affects Strongholds...
EASY enemy AI. I picked Cutter. (He was first in the list)
1. Start the game, make sure you select the Arbiter.
2. Capture all Strongholds right away.
3. Spam a force of grunts/suicide grunts and have them hang out near the enemy base.
4. Build the Arbiter if you want and have him keep the enemy from expanding.
5. Wait for the cooldowns. Stasis should take about 2 minutes, and Mass Stasis about 5 minutes to cooldown, so you should be able to do Stasis twice and Mass Stasis once in the first 5 minutes.
6. Just spam your grunt/Elite army and have your global rally point(hold in on the RS) between the enemy base and your nearest Stronghold.
7. Repeat Stasis and Mass Stasis on your army until the achievement pops! You can get a LOT with Mass Stasis.
Note: Thanks to Prophet of Lore, Stasis works on enemy buildings!
Just hang out, wait for the countdowns, spam cheap units, maybe play around with the Arbiter and try to have him easily get his anti-air kills while in Rage mode, that's super easy... or you can have him take back bases the enemy took. Or use other leader powers on the enemy for fun....
DO NOT PUT THE ARBITER INTO STASIS! I think I glitched my game once and wasn't able to use Stasis after putting Arby into Statis.. LOL. If someone can confirm that doesn't glitch it let me know, but I know my stasis, in fact all leader powers stopped working after doing that by mistake. LOL!
That's all, really easy and stress free.