If it's 15 in 15 seconds, unbuffed cat melee swing speed would cover that on its own. Fill in with abilities and it should be a joke.
Razorgore stuff:
2: Not sure what this means. It's always been able to sleep multiple ones, just the CD is about 1/3rd of the duration so you can only have around 3 at a time. Was the CD reduced/duration increased?
4: Has been in effect since 5.0 launched.