[SDPhantom]

The longest range of any normal ability is 40-45 yds. The only spells with a range larger than this are scouting spells like Far Sight and Eagle Eye. Neither of these are in the debuff category of spells you're specifically inquiring about. Not all abilities have a travel time. Some hit instantly, however those that do travel typically hit within a second of casting. If you want to make sure you allow 100% uptime, you should also account for latency. Also keep in mind that many debuffs allow you to carry over the remaining duration up to a certain percentage into the next application.