Foot-slogging=death for most of our infantry(Wyches, even Kabalites if they are advancing and not hugging cover)
Paying 400+ points for transports is a good investment in my experience. You either get a S8 AP2 lance weapon, or 12 poisoned shots that wound anything with a toughness value on a 4+!!!. If you've had to face monstrous flyers, you'll know how valuable having 12 shots(good chance to ground them) really is. My two 5 man Kabalite units in Venoms were the backfield MVP's of two of the three games that I played in my last tournament. Either of our transport choices give you fast, reliable AI or AT that is very effective for the points cost.
I haven't used the WWP after not being able to assault out of it. I could see it being used effectively by Reavers and Scourges to get access to side/ armor shots in a hurry, or to deploy reserves closer to objectives.
Give the transports a good solid look. Remember to use their full range to shoot if you aren't certain that your troops should be bailing out close to the enemy. I find that cheap, well-armed, fast vehicles can really give your opponent fits if used correctly.