wracks and grotesques

i love the models for both of these and was looking for some insight.
i've heard that running urien with grots all charged up with tokens can be very nasty.

im thinking of ordering one or two and doing some conversions from the PP warspears in hordes as per the guide.

so my questioning would be, what kind of damage can they do, are they worth it, what kind of lists would you run them in?

maybe urien and the duke as hqs... a blob of 3+/3+ warriors on foot, some venom true born cannons and adding in wracks/grots as troops?

I would love to field them but it's a lot of cash to put out to get some units that will sit on a shelf..

Coincidentally, I have given both these units a run-down in the latest instalment of my unit guide, here.

In short, both units can be very effective. If I was going to build a list around them, I'd probably run Rakarth +4 über-Grotesques in a Raider, 2x5 Wracks w/ Liquifiers in Venoms, and then top up with a couple of Ravagers for anti-armour and some Warriors in Raiders w/ Splinter Racks. If I took a 2nd HQ, it probably wouldn't be Sliscus. He is expensive, and nothing in the list capitalises on his combat drugs re-roll, so you're wasting that ability.