Are Warlock sergeants worth it?

Another thing I have begun to realise about my Eldar is the lack of anti-tank. I have Fire Prisms but they never get to shoot; I have Vypers but they want to shoot heavy infantry; I have shuriken cannon jetbikes but they always miss with a lousy BS3. The only reliable anti-tank is my Farseer with his trusty singing spear and his cousin Warlock and his Witchblade.

Against most armies they can wreak tanks as they have usually stayed still or moved only 6" and have rear armour 10 so 5 S9 attacks will almost certainly wreak something. However they are only 1 squad and against my Tau friend (who's tanks move 12" and fire) they do nothing unless they are very lucky.

So how to solve this problem. Simple take out the Night Spinner (which does nothing) and replace it by upgrading two 4-man jetbike teams with a Warlock. Who has a witchblade. And Embolden. This will make my now annoying jetbikes into tank killers; make them sub-par rather than Tau-terrible in combat and solve the annoying Ld 8 problem.

I must try this and see how it works out.