That's completely wrong point. UEF t1/t2 units land are worse then their analogues in other factions. That's practicly the whole concept of UEF where you have worse early game and better late game. I would argue that percival beats any unit.
In 1v1 aeon will destroy UEF with harb rush just because Titan is shit and Percival is too expensive and slow. Cybran have better land units till the Percival-Brick match up. Not to mention that Brick is not a lot worse than Percival and than Cybran have 2 land direct fire experimentals and rambo SCU that is incredibly strong against t3 land units. If you survive long enough to have decent Percy army and economy competitive to enemy, you deserve to win.
In team games you can use sniper bots and use air player's power to make rambo SCUs which can fight Percies better than t3 land units.
Now about experimentals. You see, UEF have no direct fire experimental.
AT ALL. How do you think UEF has to counter Spiderbot or GC?
Titans ? Percival is UEF answer to enemy T4.
Percy nerf will kill UEF land alltogether.