You say ferals are fine vs casters.
Lets compare rogue and feral vs a fire mage.
Rogue has sap to set up an opener. Feral doesnt.
Openers:
Cheap shot can be used from any direction for 40 energy, 4s stun and 2-3 CPs. Pounce is 50 energy from behind for 3s(talented) stun and 1 CP.
Ravage is garbage compared to 1-2 CP ambush for much higher dmg and 45% higher crit chance.
Rogue also has the option to shadowstep->sap a mounted/running target, as a feral u just watch them run away.
We open Pounce or cheap shot(best case)
Mage blinks.
Rogue can now shadowstep or 3 point ranged kidney shot, vanish and reopen/sap, run in front to gouge the blink or blind it. Mage most likely doesnt hit you or hits you once.
Feral has one option. 1.5 GCD+25% mana pool bear form. Then 1.5 GCD feral charge. Then 1.5 GCD+25% mana cat form. Now you can continue damage, and the mage has used 2-3 globals on you(living bomb, living Flame, fire blast - this basically kills u in about 12 seconds).
At this point the feral has no mana for shifting out to heal more than 1 regrowth+rejuv. But, you cant even do that, because the mage will just CS you.
So you basically stay in cat and spam mangle, because u have 0 ways to shred if the mage isnt terrible. Mage blast waves and his ice armor slows u every second, making him able to kite you. You only have mana for 1 max 2 shapeshifts out of Nova or a slow. And it costs a 1.5 GCD and your ENTIRE energy bar to do so.
Also the mage is free to cast because u have no interrupt.
Meanwhile the rogue has the mage permaslowed so he can never kite. He has 1-2 vanishes, 1-2 sprints, he can blind or gouge, he has better damage spamming mutilates over mangle, he has permaslow, mind numbing, he has kick. He has kidney or ranged kidney ready.
In what world is feral fine vs casters?
And yes, u could enrage into bash after feral charge, giving u an INSANE 4 sec(talented) stun. After the 1 sec bear form GCD u shift into cat which is another 1.5s GCD, leaving us with 1 global of damage before the stun is over. Yay.