Glyph Nova (Your Knockdown ability) for Increased Cast Speed and Reduced Cooldown.

Glyph Hailstorm For Reduced Cooldown (Mana is optional)

Glyph Ice Needle for Reduced Cooldown, Increased Duration and Increased Effect.

Glyph Mana Barrier for Absorption if you're getting hit too much.

No Glyphs are required for this, you can run with whatever you like, the trick is simple.

When you enter this room run in and stand in the center behind both of them. So it should be Petralisk > Crystal > Evil Petralisk > You.

Do not hit them, wait for them to stand up on their own, this will save you some time as hitting them will instantly pop them up and allow them to move. When they are up Cast Hailstorm on one and Ice Needle on the other.

Cast Nova on one and if it knocks it down attack the other. Pulse, Magma Bomb, Barrage, whatever. You can even drop a Lightening Trap in front of one.

If it knocks down neither of them, start whailing on both. Ice Needle on one, Pulse on the other, Flaming Barrage on both. The reason for this is that the key to stopping them from reaching the Friendly, is keeping them focused on attacking you.

If you knock one down, ignore it and focus on the other until you get its attention. They'll slowly creep towards the boss, but the better you get at keeping them snared and more importantly, focused on you, the quicker this encounter ends.

Sometimes RNG craps on your luck and none of your Novas knock down a Petra or your Snares don't trigger and they reach the Friendly Petra. Stand between both and Nova. Hailstorm. Flaming Barrage. Nova on every Cooldown until they are Knocked Down or are focusing on you.

That's the trick to this encounter. Keep them focused on you by attacking them. Once they're on you they'll be on you for an amount of time regardless of if you keep hitting them or not, so save your snares until they start to turn around or you wont have them when they do and start walking towards the target.