Of course. Those are ultimates.
Unfortunately, those are full of problems too.
Yes, the ult rockets chunk (and can even instantly kill, in some situations), but the combination of a small hitbox and obvious animation makes it unlikely that Heimer will ever land this, so long as the enemy knows how to sidestep.
The ult grenade is powerful, yes, but upon closer inspection it has quite a few shortcomings. The damage is only increased by 30 compared to the regular grenade, and the stun duration is unchanged. While the AOE is made quite a bit larger, the projectile speed is still slow enough that dodging the stun is not exactly difficult. In most cases, this ends up being an 80% slow on most of the enemy team, maybe stunning the enemy tank (since the third bounce is the only one that will be in range of the enemy ADC if they position correctly, they have quite a bit of time to react to the grenade).
I LIKE Heimerdinger. I want him to be good, very much so, but alas, it is not the case.