Protector's Jubilee is over and I actually achieved all my goals!
Getting the horse for my control wizard was actually very easy as renown was available in spades. I had enough for the mount after only a couple of days, bought the associated outfit for good measure and still had plenty left over.
Getting the Protector's Garden key was trickier. A commenter actually asked me how one could get the required 15 figurines in only 8 days, and the advice I gave was at least partially wrong since I hadn't fully figured out the new system yet. Figurines didn't used to be rare because you'd get them for doing the event daily quests. This year this was changed however so that the quests only rewarded purple boxes... which would grant you a figurine the first time you opened one on any given day, but that appeared to be it.
The only reliable way we found to get extras was to have other people give you gifts through the protector's hospitality, since that had a random chance of dropping a figurine, and actually more than once per day. Fortunately my pet tank was grinding the event like crazy and showered my hunter ranger with all his gifts, plus a few guildies were nice enough to chip in as well. Thanks to their generosity I managed to hit 15 figurines on the last day and got my key.
Also, my hunter ranger - the character on whom I really wanted to take things slowly again - gained about 15 levels throughout the week. There's just no way not to level fast in this game.