Ok, first off, they better reverse that change to Ultraxion. Preventing cats from shredding on the "patchwerk" of the tier is just a giant middle finger to the spec.
Or maybe it has to do with the comment that any tanking class can pick up the thrall buff by going bear/blood pres/def. stance/RF, which if it still buffs berserk would be impressively OP. You know, or they could just design the fight right (preventing cats from getting the buff is a tad harder, but simply removing berserk from it would remove the incentive).
Now, on to my point! Recently there's been a bug brought up on the official forums regarding shred and mangle-type effects.
http://us.battle.net/wow/en/forum/topic/3430807757
In summary, Shred is only buffed by mangle or trauma. Hunter pet abilities (Tendon Rip, from a Hyena), or a subtlety rogue's Hemorrhage will NOT buff shred. They will buff rip and rake, but naturally, losing that 30% on your main damaging ability is crippling.
Hyenas will only ever cast it if the existing effect (mangle, etc.) has <15 seconds, so at worst they force you to re-cast it every 45 seconds. There's also the option of the hunter turning auto-cast off, or just switching in a less worthless pet. Sub rogues are a bit more difficult, best bet is to convince them to respec or start using Backstab I guess.