Reflection changed behavior significantly in 5.1, and is somewhat unpredictable in how it interacts with different abilities. I'm trying to figure out the general rule for how it functions, so if anyone can add to this I'd be grateful.
Reflection: "Your opponent's next ability misses you and you perform the attack instead. Lasts 1 round."
What it actually does seems closer to this: it doesn't obey speed, instead it always is applied before any attacks for the round; it causes all attacks to miss the caster (this includes any direct damage or delayed damage such as Elementium Bolt, but it doesn't prevent DoT damage); at the end of the turn*, it copies the most recent attack that it prevented.
Particular cases include the following:
If you Reflect a delayed damage effect on the turn it's cast, you will prevent the application of the debuff, and you will apply that debuff to the opponent. If you Reflect a delayed damage effect on the turn that it would deal damage, you prevent the damage and you deal that damage to the opponent (including any secondary effects such as the stun from Elementium Bolt).
If you Reflect a Lift-Off on the turn it's cast, you accomplish nothing. If you Reflect a Lift-Off on the turn the opponent comes crashing down on you, you prevent the damage and you also perform the damage-dealing part of Lift-Off.
If you Reflect the second use of Pump or Wind-Up (ie the damage-dealing use), you prevent the damage, but you perform the first half of a Pump/Wind-Up. Ie, you gain the Pump or Wind-Up buff, but don't deal any damage.
* 'End of the turn' is a fuzzy concept, since many things happen at the end of the turn and although they occur in a particular order, that order isn't documented. In this case, Reflection performs its attack after DoTs and delayed damage trigger, but before the humanoid racial heals.