Some champions have very low cooldown spammable skills equivalent to flash and even deals damage (Kassadin and Ezreal, to name just the two most annoying ones IMO). They are impossible to catch without either bursting them to death with 1 combo before they can react or CCing them, and impossible to run from because they just use that skill to jump towards you and combo. Goes to show how absolutely overwhelming a champion with that sort of freedom of movement can get.
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That sort of CC can be countered with exhaust or abilities/items. A stun can delay an opponent from flashing away, or it can halt their movement after they already use the flash. Exhaust does the same; it'll allow you to catch up to or run away from them. Items such as phage/frozen mallet will slow them down and allow you to catch to them. If they flash over a wall, you can follow them if you have flash, but that's a spell that I frown upon.

Holy fuck what
Did that Soraka have ~6k HP
Did that Shaco recover most damage dealt as HP
Did our fucking AP "carries" bother building anything more than like 15 worth of mag pen
AAAAAAAAAAAAAAAAAAAAAAAAAAAAA
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Vi is some bullshit top laner. Better harass and farming than 90% of other tops.
That being said, her login screen is badass.
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Magic box god; Suck it Corbo
Lol Olimar that was the best KS ever!
Just you wait until I hit 31337 IP

Btw, how should Vayne deal with an early game hard-counter like Caitlyn/Corki? Should I specifically ask for a support that can sustain me like Soraka and just passively farm the whole time, or is an aggressive route of asking the jungler for an early gank or asking for Blitz/Lulu/Alistar to come as my support viable?
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I would just hug the turret while passively farming and ask my jungler to gank
a lot. If he ganks well, I would be able to pick up a few kills and get fed early on. In other news...

Why is Amumu so nice?
Naw, pick Rammus and
win every single game of Dominion ever.
Clearly, the most balanced gamemode ever.
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Xerath also rapes Proving Grounds pretty hard with his W + ult. Anivia too, although in more of a support-y way. The narrow lane just benefits quite a few champions with good AoE.
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AFAIK balance decisions are made only with Summoner's Rift in mind, so it's no surprise ARAM/Dominion gets overrun by a few champions.
@poison: No one plays Dominion competitively (at least I hope not), and it's hilarious to get to the windmill 5 seconds before the enemy team gets halfway there.
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Just played one round of ABAM. It's total bullshit.
Nidalee/Lux/Jayce both teams, and the champions that weren't on both teams were all poke champions like Xerath (I was Gangplank, so I guess that counts as a poke champion too?) No wonder nobody plays ABAM; it's pretty much the same OP champions on both teams every single time as a poke-fest.
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Either all random or draft pick on that map. Blink pick is terrible for that. With draft pick at least both teams can't be the same and you can try to counter-pick, plus you can ban some champions.
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