Enclosure posted...I dont know about you, but my enemies don't conveniently all stay together in one spot. Rarely are they clumped enough to get more than 3 people in the ult range, and one of those is usually at the edge far enough to simply take one maybe two ticks of it then walk out.
its a pretty small area that it effects. Unless you have an orianna vacuum following you, hitting everyone just doesn't happen.
I chase the AP carry for a taunt, which usually gets the aggro of the enemy ADC as I'm the closest target, and a bruiser for peel. If nobody tries to answer me, I just take out the carries. If they do, they're all staying in range.
You can force them in range by just being such a dangerous target that someone HAS to come deal with you. Aside from his initiate, Malphite's natural 20% AS debuff combined with a Randuin's or Frozen Heart makes him a great anti-adc that SOMEONE needs to peel. It's the same effect with Leona. She has enough disables that she can take an ADC out of the fight long enough for just about anyone to drop them. It's what gets a tank focused, or disabled long enough that they aren't as big an issue. It's why Rammus, Amumu, and Malphite are such great tanks. They do enough to the enemy team that you need an answer for them, which is generally to focus them down or disable them. All 3 of those however, have a way to make an effect on the teamfight while stunned, or keep from being stunned (malphite ult, or the aura effects of amumu and Rammus).
Some teams this won't work, like with Irelia who is just going to leap to your carry and kill them, or Renekton who will do the same. But with a team comp focused around forcing the fight in your terms, such as your own Irelia or Renekton or Jayce or Vi, who can dive a carry and eliminate them while you rack up enough damage to be a huge threat... They just HAVE to answer you, and running isn't always an option.
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Now these points of data make a beautiful line, and we're out of beta we're releasing on time! So I'm glad I got burned, think of all the things we learned!