So, I'm going to try to explain this for all of you that are concerned about this incentives thing not giving deeps a shot at the CTA rewards.
For any given group you need:
1 tank
1 healer
3 dps
Taking those numbers, let's make an example of an LFD "toon pool". The LFD currently has:
9 DPS
9 Tanks
9 Healers
With this pool you get 3 full groups and still have 6 tanks and 6 healers left. That takes tanks and heals off of the CTA and puts DPS on to encourage more so that the remaining tanks and healers can go. Now, according the post by Bashiok this is an ever-changing system so there is really no way to know just how many times any role will get CTA but, you can bet that DPS have an advantage given how many are needed per group.
Hopefully, this will help some of cool down a bit by seeing numbers instead of just mounts and pets.