So a lot of people are only looking at Senna's positive traits, as people often do. "Senna is gonna be sick nasty broken OP" "You heard it here" "Day one insta-ban" "Riot just trying to milk the game :\". However, people are conveniently ignoring her massive, and I do mean massive, downsides.
Free damage. Range. Crit. omg omg omg so busted right?
Not quite. For one, Senna's crits deal _35%_ less damage. 35%. That's a huge negative to her critical power. Even with 100% crit and infinity, she's never going to hit as hard as a normal ADC. In addition to this, Senna gains _no AD per level_. None. Zip. Zilch. She is entirely reliant on her soul mechanic to keep pace. If Senna fails and falls behind, she can't just buy her way back into the game with a single item power spike. Excessive crit does add to lifesteal but we're gonna hit another point with that in a second. Senna also only gains 25 attack range per stack of 20 and has a base range of 600. Annoying, maybe, but she needs at least 80 stacks to get some absurd range. Unless you buy RFC?
#Senna's Base Stats
One of the things _nobody_ seems to talk about is the proverbial wind-up on Senna's auto-attack. As Riot August said: Most champions have between a 0.2/0.3 delay on Autos from animation-to-shot. This matters quite a bit in terms of orb-walking and getting some autos out. Senna's autos have a _0.5_ second delay. It takes Senna half a second to fire. And no, this isn't improved by attack speed. Senna is a sluggish shooter with her gun which trades off her powerful damage (% current HP on hit) in favor of an admittedly questionable attack speed. She's also got some other meh stats befitting a support (330 MS and 520 HP, oof)
Senna's E is grossly misunderstood. Everyone is under the impression that it makes people invisible, untargetable and hair-raisingly difficult to kill. This is not the case. While it does turn allies "invisible", it's more of a moving bush than Pyke's W. At all times you can tell where Senna is and when allies exit, they can still be hit by skillshots. Think of it more as "I am a giant vape cloud and nobody can tell who is in the vape cloud". Expect this to be something people don't understand.
The giant array part is the only part that actively shields. The singular, tiny center beam damages people. Expect a ton of shields but not so many snipes with it. Not much to add here.
Senna doesn't have the makings of an ADC. She's sluggish, deals moderate damage and is entirely reliant on her mist passive to scale. In addition, while I didn't mention it above, Senna's scaling on her abilities is...meh. A ton of her ratios are siphoned by her supportive abilities so even if Senna becomes a major damage threat, she's always going to lean more on the utility part.
My guess is that people will attempt to take Senna as an ADC or a "Support" like Lux and build glass cannon. There will be some success but most will botch it and cry for buffs because Senna has so much of her ADC budget siphoned into her supporting tools. People are likely going to call her clunky because her shot delay is different from most champs.
All that said, I do think boards is right in that this is another champion which further strains the bounds of Pro play vs. PUB play. Once again, a cool design is hamstrung because (CHOOSE YOUR ENDING)
* A.) ...riot continues to care about 0.0001% of pro players and high ELO.
* B.) ...riot continues to cater to know-nothing casuals.