I definitely see your point! Here is my strategy with Vect's unit:
1. It is now T4 against shooting. Could be helpful against Bolters, ect.
2. Cheap way to get a Pain Token, and another Dark Lance/Raider.
3. I've been running Vect with a unit of 7 to 10 Wyches, and they will eat through whatever they charge, leaving them exposed to getting shot to pieces. Now, hopefully I can end combat on their turn and will then be able to move into cover or assault another unit.
4. One of the greatest pieces of wargear in our codex: Obsidian Orbs. Follow me on this. Besides the fact that it absolutely murders Marines (I've wiped out whole squads) it heals wounds that he has taken. As long as whatever is hitting him in Close Combat allows armour saves and wouldn't cause Instant Death, I take the 4+ Armour save and the 4+ Feel No Pain save instead of the 2+ Shadowfield & Feel No Pain. Will a wound or two get through? Probably. But he has four, and when you wipe out their unit on their turn, hopefully another target will be within range of his orbs.
If you want to get mean with them, put Torment Grenade Launchers on his Raider, park it beside an enemy unit, disembark, throw the orbs, and then assault. TGL will ensure that any unit outside of one with an IC will be wounded on 2s.
5. Like you said, he is a lot of points. I don't want to add to that cost by attaching him to a 100+ pt unit, the Wracks cost 70 to 100+ points cheaper than a Wych unit. (But don't get me wrong, I love my Wyches!)
Anyways, the English language does not have the words with which to describe the pure joy I feel when my fearless leader massacres squad after squad after squad of Marines, haha!