Under 34 and you will mana-screw constantly
It lets players put a specific card from their library into their hand and then discard a card at random, potentially losing the very card they desired
The proper buying window on rotating cards is hard to nail down because its difficult to properly account for where most of the demand is coming from on multi-format staples
Hunting Velociraptor gives your dinosaurs prowl, which means if you have dealt combat damage to your opponent with a dinosaur on a given turn, you can cast it for just three mana
(Choose any number of permanents and/or players, then give each another counter of each kind already there.) If High Perfect Morcant enters at the same time as one or more other Elves you control, its first ability will trigger for each of those other Elves as well as itself
So many cards make it easy enough to accrue counters that Soul Diviner can turn into a rather potent engine, with the only drawback being that it needs you to play certain cards in order for it to be powerful