Let's talk about the Wave Serpent itself for a bit. It's AV 12 on the Front and Sides AV 10 in the back. It's also BS 3 like most Eldar vehicles and has a carry capacity of 12 models (or 5 Wraithguard and a Warlock) It supports a single Twin-linked weapon from the Eldar Vehicle Armory from Shuriken Cannon to Brightlance and has an underslung Twin-linked Shuriken Catapult which may be upgraded to a single Shuriken Cannon. In addition it has the option of taking all the standard vehicle wargear save Holo-fields. It's a Fast Skimmer Tank with 3 Hull points, with all that said it gets better. What makes the Wave Serpent unique is it's Energy Shield/Prow/Field. I don't mean to repeat the codex entry here, but it knocks down any shots strength to 8 and negates any form of bonus dice to the penetration roll (including melta, ordinance, rend, etc.) Now the catch is that it only covers the front and sides of the vehicle and doesn't work in melee, but what it means is that no weapon has better than a 4+ to Glance or Penetrate this tank.. unless you expose your rear.
That's what keeps it alive folks, a 50/50 shot that your lascannon/missile launcher/doomsdayblastersmasher can do damage to this thing. Back in the day, before Hull Points Holo-fields were king and far superior in that yes, you would get damaged, but more often than not it was a shaken or stun. With Hull points and the change to glances, Holo-fields are significantly less favorable and the Wave Serpent with it's Energy Field wins out, but wait it gets better. Jink! You get a jink save! Now your opponent can only deal damage to this tank on a 4+ or worse, but you get a 5+ save against it. Punching these numbers into the ol'Mathhammer machine and you're looking at a 22% chance of taking a hull point and only a 2.5% chance of being destroyed. What happens when you move flat out? More survivability! Added bonus with the new rules for glancing hits, it doesn't spend the whole game shaken and even if it was you could still snap shot!
Have I sold you on the Wave Serpent yet? Well let's sweeten the deal. I give you the Metagame Vehicle Continuum.
My local Meta Game appears to be somewhere between Nobody Brings Vehicles and Nobody Prepares to Face them. Case in point in my last game I only had to worry about Thunderhammers, Powerfists, and a Vindicator Tank and I had Four Grav Tanks on the field, at the end of the game I only lost one due to poor positioning. My point is there will likely be a point, and this is my reading the Runes of Fate a bit here, that you can bring numerous amounts of vehicles and your opponent won’t be able to handle them, hull points or no. If you can hit the sweet spot in your meta, in addition to the survivability of the Wave Serpent I illustrated above you’re sure to get some extra life out of an otherwise expensive transport in an outdated codex.