She has a short range sticky bomb that also has a tiny explosion radius of 2 meters and only does 400 damage.
Compare that to the other explosion ults:
Pharah summons a rain of 35 rockets per second each doing 40 damage.
Junkrat summon a tire that you can control from a far, does 600 damage and has a 10 meter radius.
D VA has the king of ults with a 1k damage 20 meter explosion that also knocks you back if you somehow manage to survive.
They really need to buff Tracer's shitty little cherry bomb, whenever I see her ult pop up, I don't get the excitement I get when I see any one else's ult pop up.
As far as I can tell EVERYONE has a game changing ult. As in an ult that can literally change the course of a fight. Tracer's ult is good for killing maybe 1 or 2 people if they are close together and I manage to stick the bomb to one.