HARBINGER: if you make harbin slightly slower, better all around, and more expensive, you can fix your issue, it would be a great unit if it was tweaked here and there so it was worse early game and better late game.
Beetles/Mercy: i think these are fine, they make for funny cast, face palms of all types, and they separate good and bad players.
Rhino(and Othuum) I think changes to there dimensions would be great, rhino could also use a little more speed, and othuum should have more range on the side bolsters (in accordance to the harbinger buff)
experimental bp is fine, megalith reclaim is already op.
sera sacu is generally agreed to be the most micro dependent, i think making it more expensive but still a counter to experimentals would be nice, because leaving a Ythothia next to your line of shields and pd doesn't usually work
As for Uef sacu, if you just nerf range it won't be enough, it can kill 8 ilshavohs in about 2-3 seconds with its current aoe, damage combo, you have to nerf those too.
as for cybran, it would be nice if this was geared to be a solo unit, since monkey lords already handle lower techspretty well.
as for shields on trans: interesting, but right now not important enough to take a look at.
edit: Titans could use a buff i guess, but i always thought they were as worse than the cybran counter part because the percival is better than the brick [brick has better fire rate, but once you have enough percival (0r if you mix in titans) than its fine]