No reason to use Boots of Swiftness on Singed when you have movespeed quints + utility movespeed thingy. If not Mercs then Ninja Tabi give you defensive stats and dodge, which combined with that defense tree dodge mastery basically give you 10% extra movespeed when you're poisoning minion waves.
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"Getting lucky 100% of the time... it's called PRO SKILL."
-BlAcK TuRtLe