Well, based on the data we're getting in so far, seems like part of the problem is that the first day of school nerf might not have made the card weaker?
Still included in 95% of paladin decks.
Hard to get drawn winrates isolated from the old FDoS on HSReplay, but we can get played winrates post patch. Now, yes, played winrates are a dangerous metric, cause they overvalue finisher cards like Alextraza and sometimes rarely played cards get overvalued cause they were played in one variant of a deck that had higher winrates than other decks. For example, Shadow Hunter Vol'jin is in the top 5 played winrate Paladin cards, but...that's from playing it in a goofy combo deck when things go right, and it's only in 7% of Paladin decks. But none of these caveats apply to First Day; it's not a finisher and it's played in every paladin deck. And despite all that it's still top 10 post-nerf for played winrates among paladin.
So...yeah, First Day might not actually be weaker. (Which means it's probably actually stronger in more midrange decks like Libram Paladin). Combine that with Crabrider not being in every Paladin deck pre-nerf (and not actually getting nerfed that hard so a lot of people still run it) and yeah...Paladin's sayed pretty constant.
I didn't read this yet, but wanted to respond
I think it's weaker against faster matchups (Hunter, Druid) where you generally want to play a 1 on 1 to get the board against them, but against slower matchups it's still... pretty good, since you use it as a refuel instead of a tempo card. Libram Pally also has Hope which kinda solos those aggro matchups.
It's like how Twin Slice had DH go from Tempo to Aggro. Pally seems to be going more value based, starting to see some N'Zoth builds pop up too with Gryphon and the Elemental 6/6, Murgur/Redscale, the Dragon Cairne etc.