Yeah cybran is op on this map you can do tons of stuff :
- Best T1/T2 navy to rush & deny ANY naval early
- Torp com
- Stealth subs
- HARMS creep with SCUs (or early with ACU)
- Monkey/Mega rush into ennemy base
- Telemazer
- Scathis
- Soul Ripper
- Really annoying TMLs
And as stated above other faction have nice possibilities too.
Sera is nowhere near OP on water of isis, you probably need to learn navy balance better or just how to counter T3 subs in general.
If sera is low on T1-T2 to go fast T3 you should easily win before he gets a lot subs. If it is 3v3/4v4/ then teamwork matter more than the doing of a single person probably.
I am not sure when I say this, but it seems interestingly difficult to counter Cybran OP SHIT (T1/T2 rush / T3 harms spam / insert favortie tactic here) if you encounter a Cybran player who knows how to play and get to the T3 stage in Waters of Isis? (Total sea domination means that losing the sea is as good as losing the game on that map?)
Any land (hover tanks) and sea form of attack will be hard countered by T1 frigates + T2 Destroyers + SoulRipper/PDs? Any attack from air will get knocked out by any T1/T3 Interceptors, Cruisers/Aircraft Carriers and Static AA defences? The Cybran player thus has the advantage to do what he likes (T1 or T2 navy rush, wagners, T3 Battleship, Experimental walking base to base, scathis or Nuke?) as long as there are enough of the op HARMS heavily mixed with sams/tmds/sacus/navy for defence or to push an attack?
If you do not attack, you allow Cybran to get to HARMS spam and you lose. If you attack, you will give Cybran reclaim and still lose top op T1/T2 navy? It seems like Cybran has the advantage on this map from T1 to T3 ?
Is there any decent strategy by which the other factions could use to counter this?
You probably can do that for ANY faction. You don't provide any concrete material that would allow us to help you : saying "XXX unit is too strong" without providing replays or telling us what you tried.