Chimeras a pretty powerful for a Reams of Chaos warband, so I've opted to use the least of the profiles you can generate and offer no bonuses for the heads, tail, etc.
Toughness 5 and Wounds 5 is going to tough to bring down but the creature only has a Leadership of 7 so Threefold will need to be careful of the creature's deployment because it may be easy to frighten away! Luckily, the Tzeentch champion has wings and will be able to use them to match the creature's mobility.
Shrug - not too concerned about it at the moment. If the monster proves too powerful I'll save it for Warhammer Fantasy games...