This is exactly the reason why i'm so undecided about the rippers. What do you do with them when you are facing off against elves? Can you send them into warlock for example? You really don't want to be too dependant on magic to buff the eaither...
I've only used them against elves once, the forest variety, and I marked his mage's unit with a toad. I didn't expect them to live and didn't expect either unit to actually make it to the mage but it forced my opponent to play reactively and keep the mage in his deployment zone for two turns. I would try and either go extreme flanks, they'll eat fast cav decently. Or mark the mage/bsb/juicy target, deploy in a single file and charge in so you touch the actual target in the unit, at worst 8 models can attack and that should leave at least one Ripper alive to do the job, KB not needed really, you can kill a T3 mage with 5.5 (rider) attacks
This is pretty much all they are good for against elves. If they manage to kill something, that's just great, but in the end, their primary purpose will likely be pure target saturation and the sheer fear of facing a squadron of lots of attacks with KB, which he has to know will be dedicated solely on his character. Most people tend to overprotect against these. I once toaded a unit of 30 grave guards, and instead of sending them into combat, he kept reformming to face me, and I kept making the Ld roll to avoid charging, and simple reposition so I got a flank or rear charge. At the end of the game, my Rippers hadn't seen combat, but neither had his Grave Guard (He gave up turn 5 but wasn't in a position to charge, so he reformed and moved towards the fight - and turn 6, he failed his charge on a 5 where he needed 7.) All in all, the rippers aren't there to kill. I've found their primary goal is to pressure the enemy. They are unlikely to accomplish much (Though they ARE good warmachine hunters), but most opponent WILL react to a unit that can easily pump out 20+ KB attacks. That's scary for almost any character who isn't invulnerable to KB.
I made a StegadonSh*t list which I nicknamed 'Pirahnas of the Air' This was the list: 1 Skink chief on foot 6 Skink chiefs on Rippers A F***ton of skinks (Can't remember quite how many) 3 units of 10 Rippers I went up against my Dad's Brettonnians and expected to get smashed, instead I did better than I had done in any previous game against him! At one point I had my one of my Ripper units charged by the Knights of the Realm, and expected to get massacred instead he got the rubber lance and caused 3 wounds, They had a Blot Toad, it took a 2 wide frontage of Rippers 2 rounds to kill the entire unit, in the front.
I just had a game versus bretonnia as well. Put 3x3 rippers on my list since KB is just amazing vs cavalry. I won the vanguard roll, and knew the bret player would make the mistake to Pray. This allowed me to position my rippers to awesome flank + rear charges, behind enemy lines. So my next turn I charge a 12 man Kotr buss with 2x3 rippers to the rear and to the flank. The whole unit is wiped out from 9 KB and 10 normal wounds. Another Kotr bus was wiped out by 3 GW scarvetbuss. Epic game
I really think the rippers should've been given something like an initative buff or ASF when they attack a toad target. They're a bullet, but what good is a bullet that doesn't get to hit before it dies? Atleast stuff like Wild Riders have a high initative and ASF so they're pretty much guaranteed to do their thing. Rippers have poor Ld and poor initative. They do the same job for the same amount of points, but they're so much harder to use.