From the pocket pick that was Senna with Grasp to the tank Senna with Glacial augment, she has been an annoyance on the Rift for quite some time now. Riot intend to make her one this season as well.
Senna is League of Legends' first-ever marksman support champion, with a story that connects to both her archnemesis Thresh and her husband Lucian. A story that was, ironically, ruined, with the flop that was the Ruination event.
However, that is not the only frustrating thing about Senna, not by a long shot. If you've played League of Legends at any time in the last two years, you may have chanced upon tank Senna in the Rift, one with an incredible amount of slows and nigh unkillable. these new changes may just bring that back into the meta.
With the upcoming League of Legends 12.2. patch, Senna is getting buffed by Riot, with slows in mind:
"Senna has been a bit weak in the new season so we have a buff going to PBE soon:
Q- Now slows enemies by 20% for 2s. We felt that old glacial did a lot for Senna's pattern, especially as a support marksman, so we're trying to add a slow back onto her kit."
Coupled with the new Glacial rune, which lays unused for now, and not for long once the meta establishes, Senna sill be an untouchable kiting machine, that can just as well run you down, all the while healing her allies and damaging her enemies from half the map away with the range from her stacks.
At least, that will be one marksman assassins won't be able to delete instantly, though.