A combat trick is a very powerful way to get card advantage or removal, even both sometimes, alongside gaining tempo
Serrated Arrows were playable for the same basic reason that Aeolipile, Nevinyrral's Disk, or Quicksand were playable
Invasion of Shandalar / Leyline Surge Invasion of Shandalars effect is a decent enough recursion spell, but if you manage to transform it (and keep Leyline Surge from being destroyed) you can cheat any one permanent in your hand onto the battlefield per turn, which can be absurdly good
From what my mom told me, I mustve sat there reading it for hundreds of hours, since I was able to basically memorize what every card did from base set to fossil
It doesnt look like theres a whole ton of cloaking in the set, which means it will probably be fun and special when it does come up