Hydromancers, if that's what we're calling water eles, are fine in both PvE and PvP, but for different reasons. In PvP, you should run a Water Ele/Necro and use mass hexes and snares to hold the other team still and reduce their effectiveness. The first team I ever took all the way to HA (from RA ... four elementalists!) featured me as a water hex mage (ele/nec). The others were spiking/interrupt (air/mes), nuking (fire) and warding (earth/monk) ... that's right, all four elements.
The key is to remember that you're not there for damage. Oh, and focus your wrath on their warriors!
As for PvE, water can actually be used to pressure spike in some areas, using dual attunements and ice spear for a continuous 74 damage (mitigated by armor, of course) against a single, preferably soft, target. Throw on blurred vision and Mist armor to keep from being ground down by warriors. Vapor Blade can also be added as a finisher or opener for the spike stream. Just don't do this is PvP.
That being said, you'll never be as good at spiking than other spike class builds in PvE, or as good at shut down as a mesmer (although you will shutdown more at once) in PvP.
