I think that the bigger problem is Syclant, considering that Revenankh can merely be phazed away if it's not the last pokemon and it doesn't start to do that much damage to walls until it's got 3 or more Bulk Ups. That would simply be another case of letting somebody set up on you. In addition, Revenankh is not invincible in the least, and it takes a very large amount of damage from pokemon like Yanmega and Jirachi. Honestly if Metagross starts running Zen Headbutt more or Zapdos needs Metal Sound to take it on, that's just a metagame shift. If Gyarados was removed a whole mess of things would change.
Let's look at Lucario, who is now one of the scariest OU threats around. The Swords Dance threat hits ridiculously hard, and Luke has only 110 Attack and 90 Speed. Syclant, who arguably has better attacks, has 114 SA and 121 Speed. The secret to the success of both, of course, is the enormous base power. I think that STAB Blizzard with Tail Glow is just too damn good. Ice Beam has been considered one of the best attacking moves in the entire game, and yet it apparently wasn't good enough for Syclant...
However, I'd say that the worst part of Syclant is not Blizzard, but Focus Blast. Giving it this move, in my opinion, is comparable to giving Revenankh Thunderpunch, removing Gyarados from its list of checks (in this case we took the smart approach and denied the move to Rev, which I believe was significant). I think we had a perfect opportunity to make Heatran a counter and we kinda blew it. One aspect of Lucario that makes it possible to handle is its move conflict. If it runs Crunch, Gengar outspeeds it and sleeps/kills it. If it runs Bullet Punch, Cresselia and Celebi can handle it much better. Syclant doesn't really have the same conflict at all, Focus Blast just fits right in. It smashes Snorlax, Blissey, Heatran, Forretress, Scizor and Magnezone, who would otherwise do fine against Syclant in general, except for *maybe* Forretress and Scizor. Earth Power is also an issue, for it hits Tentacruel who is the only pokemon in OU that resists Ice/Bug/Fighting, and it's yet another way to smash Tran and Zone, although I don't think it's as large.
If we were to give this 115 Speed or lower, get rid of Compoundeyes and not have Focus Blast or other suspicious attacks, I suspect that we'd see a massive improvement. Currently there is no pokemon that can actually switch right into an unknown Syclant and make it leave 100% of the time. The closest thing would probably be Scarftran, who is also risking the possibility of sash. On the other hand, if it has no Focus Blast, I could see Blissey and Snorlax reliably countering Syclant. It's now outsped. Ice Beam is powerful, but not nearly as threatening to even things that resist it like Blizzard is. These are not neutering issues in the least. Life Orb Gyarados is considered one of the most powerful sweepers in OU, and yet there are several pokemon that can switch right in and scare it away.