Like I said, it's extremely difficult to justify not getting 1-3 of these things. I've faced them on two different occasions now and they melt any backfield scoring unit and put so many wounds on other units with their re-roll everything you just kind of sit there scratching your head when you realize their point cost.
I just want something to replace my Griffons...So seems this fits the bill nicely. I always thought Griffons were underrated, but Wyverns seem better and cheaper. GW obviously want to shift the new models, hence they are so cheap.