Is Rek Sai's ultimate kind of bad?
At first glance it seems great! Teleport anywhere on the map...
...that your team already has control over, or to a location that is so unimportant that nobody bothered to pass through.
Its probably at its most valuable in lane phase, when the controlled zones are very small, but as the game goes on, one team is going to have more map control, and thus are going to be trampling your little holes all over the place. I guess the idea is to be sneaky and plan ahead of your oponents and hide your holes in fancy places... or you could just pick
and have everything in the game except an unreliable global teleport that announces itself to everyone on the map.
So yeah, global mobility ults great, reliability even greater. There are plenty of junglers with powerful ults that arent dependant on someone not standing on your exit for 2 seconds. Would you rather have
or
ult into your lane?