By default, Poison, Burning, and Bleed effects last a set number of seconds, dealing damage each "Tick".
While Poisons and Burning can be extended by reapplying the buff, bleeds cannot. All three can, however, benefit from traits, runes, and sigils that increase the duration of a specific debuff.
For example, the 2-piece bonus for the Rune of the Balefire is 15% burn duration. If you then look at a skill that usually applies a 1 second burn, you'll notice the tooltip now lists it as lasting 1 1/4 seconds. (It rounds to the nearest quarter second increment).
My question is, does that extra 15% of one second actually increase the number of times the condition ticks and deals damage? Or do I need a full second for there to be an actual increase in damage / ticks?