I find all of it to be pretty good except this:
Passive: Fast Learner
Every time Joshua is killed by an enemy Champion or gets a kill/assist he gains 2% tenacity, 4 movement speed and 2.5% cool down reduction. Stacks up to 10 times.
At max stacks (10 death+assist+kill), a value that isn't that hard to get, he gains 25% CDR. That's more than any item in the game can give you (Validation needed) and is more than halfway to CDR cap. So either you reduce this and make buying CDR have some value, or he ends up with naturally high CD's to balance with the capacity to only buy 15% CDR without wasting gold.
Of course, this is just my take on it, and I could be very, very wrong.