It all started with the Aimed Shot change. Aimed Shot was the hunter's MS in WotLK and was later changed to Widow Venom because Aimed Shot was going to be a MM exclusive ability. Aimed Shot was the same as Warriors and Monks MS today, a core ability that does damage. This would change with Widow Venom introduced.
Widow Venom is the result of the failed venom system back in Cataclysm beta. While it seemed like the old sting system in Wrath of the Lich King, it was eventually removed. They kept Widow Venom as the last remaining venom and haven't altered it since.
Widow Venom is not like other mortal strikes. Warriors and Monks have theirs tied to a main ability. Rogues have their MS passively, with Wound Poison. Now we get to hunters and their MS. Widow Venom is an ability that costs 15 focus, does no damage and is on the gcd.
Some may say, 15 focus isn't that bad right? If the debuff wasn't a 10 second duration and on gcd that might be the case. If you want to have a 100% up time on the debuff it results in 90 focus lost per minute. That means hunters lose 2 Chimera's/Kill Command's (and about 2 AiS), about 4 Arcane/Explosive Shots, 4.5 Tranqs or a combination of all of them per minute.
Focus is a resource that doesn't just come passively, like energy. Hunters have to cast to get focus as well. That is why it isn't a fair argument comparing an energy costing interrupt to Widow Venom. Hunters lose a lot of their resource keeping Widow Venom up, when other classes essentially get it for free.
So how can Widow Venom be improved? There have been many ways suggested to fix this issue. Widow Venom could be changed into a passive. The passive would act just like the Marked for Death Glyph (Chimera Shot, Explosive Shot, Arcane Shot and Kill Command apply it). On the other hand, the passive could be that autoshot now applies Widow Venom.
If the ability itself doesn't change, there are others ways to alter its effect. As much as some hunters like our PvP glove bonus (2 seconds off Trap CD), it could be changed to effect Widow Venom instead. The glove bonus could be that your Arcane Shot now applies Widow Venom. Since all hunter specs use Arcane Shot, it would be the most logical choice without making the bonus too wordy.
A last resort idea would be removing Widow Venom entirely. With a MS gone, hunter damage could be tuned like classes that don't have one.
So that leaves it to everyone else. What are your thoughts on Widow Venom?