After some testing done by others, and I double checked and found this to be true, you do not actually need +100% duration to get Barbed Precision to tick a 2nd time, nor for say a 5 second bleed to tick 10 times. It is rather more random, and can happen with less.
Only on the very first application of any condition would this be necessary. As the way condition damage works, once the first damaging condition is on an opponent, it starts a timer of when condition damage will tick, and all furthering conditions then must adapt and hold to that same timer. Think of a combat length as in segments like that are on ruler, and lets say the first bleed is applied at 1.5 seconds into the combat, the first tick will happen at 2.5 seconds, then 3.5 seconds, etc. So if we then use a second bleeding ability (say Barbed Precision) and it lands at 3.0 seconds into the combat, it will first tick at 3.5 seconds, then again at 4.5 seconds, etc. Following the exact same time segments set by the first bleed. Therefore, if you have only +50% duration, you would get two ticks in this scenario - because at 1.5 seconds length Barbed Precision, it is enough for it to cross 2 tick points, due to that it started counting halfway past the last tick.
What this means for the bleeder build is that 90% duration is not really way worse than 100%. Outside of the first bleed which will set the timer for all conditions, 90% is like it should be, only 10% less effective than 100%.
Terror damage which ticks off Fear works the exact same way, and that is why sometimes Fear will tick twice on damage even if you have less than +100% Fear duration.
To give an example, if your bleeds do 100 damge per tick, and you get 10 Barbed Precision proc's in a combat, at +100% Duration, you should expect 2000 damage from those procs. While at +90% duration you should expect 1900 damage (roughly on average). 80% to be 1800 damage, etc on down.
The way they have done this system is actually quite fair and means that extra duration is not wasted, or an 'all or nothing' propistion if you just fall short of hitting some magic number like +100%.
I hope this was not too confusing and is understandable. And perhaps helpful.