I've been enjoying Tracer in Heroes of the Storm quite a bit. I tend to play for the daily quests, which has unfortunately not popped up for Assassins lately (and I doubt there will be a "Play as an Overwatch hero" quest for some time) but I've been doing some "extracurricular" games on Tracer, and I'm beginning to appreciate how powerful she is at taking down enemy heroes.
She definitely has her weaknesses - she's very squishy and if she's stuck in a lane by herself, it's going to take her forever to clear a wave of minions, as she doesn't have any AoE except Pulse Bomb and one talent I'm aware of that affects Melee.
But against heroes, holy crap does she shine. The latest game I played, we had a total of 33 enemy takedowns and 16 of them were my doing.
The main reason for this is her mobility. She can keep pace with a fleeing hero and continually barrage them with damage, which immediately means that the usual "first you've got to catch up with me" strategy for fleeing isn't going to work.
Blink then allows her to close distance to make sure that she's always in range of the fleeing adversary, and Recall allows her to even overextend into enemy territory for those last couple points of damage and then get back before the towers shred her.
I've also started to get better about using Pulse Bomb. I may have neglected to mention this in the post where I went over her abilities, but this is a sticky bomb that will attach itself to a target - it's a very short range (improvable with a talent) and certainly a skill shot, but if you blink in close to an enemy and pop it onto them and then Blink/Recall back, you should be able to stick it without too much difficulty, and especially if there's a crowded team-fight going on, this can really do some devastating damage.
Tracer is not an easy hero to play - she might demand more actions per minute than any other (though Lost Vikings might beat her.) One thing you'll have to manage a lot is making sure you're targeting the right enemy - she can be locked on to someone out of range and thus ignore a closer target. And of course, Blink is very powerful, but only if you can aim it correctly. Recall has a bit of a cooldown, so you'll want to be aware of when it's available and be ready to use Blink as an escape rather than pursuit tool in case Recall is not available.
And one last thing, because Pulse Bomb is charged using your own actions and can be made to charge much quicker, I'd recommend using it frequently and not simply letting it sit on your action bar. It'll take a nice chunk out of an enemy hero's health, and can potentially do some very large AoE damage.