Speed secondaries do need to be balanced, there really is no arguing that. No other secondary stat is so high compared to its value as a primary stat or the set bonus the related set gets.
And people having spent money, time or effort on a thing is no reason to not balance it. Balance is about what's good for the game - currently mods with high speed secondaries are clearly the best mods in the game by a long way; that needs to change.
Of course if this does happen it needs to be proportionally changed similarly to how the health and def flat primaries were rebalanced before. The new values should be similar to the increases gained from other secondaries: <1000 health or <10% def is sensible and doesn't ruin intended character design; something that amounts to a 20% speed boost per mod even to fast characters is way too much.
