Personally, I dodge AT LEAST once a day in ranked, often even more.
I look at it as if I'm not AT LEAST 60% sure of a win, I dodge. If I'm countered by 4-5 of their team, I dodge. If my team has an obviously tilted member, I dodge.
Doing so sometimes loses me more LP or time than the game would have(3 dodges in a day, for instance, is -26 LP and -65 minutes), but it doesn't lower my MMR like a normal loss. Due to dodging games that I'm SURE are losses, I've got my LP loss down to 14-17 per loss, and up to 23-26 per win. It really does pay off. If you KNOW that game is a loss, dodge the thing, don't waste your time.