TMek7:

Here's my list of how UNSC is OP compared to Covies:

• Anders hawks cost the same resources and pop cap as the vampire (eventhough hawk is more effective).
• Anders has insta-air-kill leader power (annoying against the only thing thats good against hawks).
• UNSC has leader power, D-bomb, Healing, Pelican transport, super unit upgrade, Vulture, ODST drop (cutter), half price and speed upgrades (anders), other eco boosts. While Covies have Scarab, hero unit, leader power (in range of hero unit and not in D-bomb), grav lift transporter, shield generator building. These things don't match up equally.
• Warthogs... scout units? more like mainline assault. Scouts are supposed to scout bases, not destroy bases en masse!

Easy to fix:

• Increase hawk pop cap cost to 3 and increase build time.
• Make vampires immune or more resistant to the cryo bomb.
• D-bomb should take longer to recharge.
• Nerf the warthog's damage to ghost strength atleast.
• Increase the vampires strength against air units.
• Decrease the hawks/hornets strength against air units.
• Increase the banshee effectiveness a little.
• Increase the covie units build time or upgrade speed by 15%
• Dim the sword lights on the honour guards while invisible.
• Increase the grunts damage to air units with the needler upgrade.

The D-Bomb is the only way the UNSC might be OP, but  the fact that the Covenant have a leader like the Arbiter makes everything fair..

Hawks are freaking hornets upgraded to the MAX, of course one of them can take down a Vampire. But if the Vampire uses Statis Drain, the hawk would be history