Super speed gives 35 feet of stealth. Coupled with Shadow Cloak (35'), you're generally well-protected against detection from anything short of Giant Monsters & Turrets (100'), sniper-type enemies (149'). Putting a Stealth IO in brings you up to 100 feet of stealth, so as long as you're more than a foot away, giant monsters can't see you. Activate Nebulous Form (cyclic 20' of stealth) and even GMs have a hard time picking you up.
At that point, the only things spotting you are sniper-type enemies; as well as Knives of Artemis, Rikti Drones, and Rularuu Sentinels (All of whom flat-out ignore Stealth)
And ambushes, because they always know exactly where you are.