I made this post to confirm Darthmufin's original hypothesis that Vauban's grenades inflict 15 Blast damage on impact. In the following screenshots, I don't have any power strength mods equipped; the damage values displayed represent base values. I also have a rank 0 Tesla and Bounce equipped in order to see if fusion has any effect on the damage on impact (turns out the damage is constant regardless of rank). So if you're curious about the "80" that shows up in two out of the three screenshots, that's the electric arc damage of a rank 0 Tesla.
As chargers are neutral to blast damage, grenades will only deal 15 damage on impact.
Healers resist 50% of the initial blast damage, resulting in 15 x 0.5 = 7.5 final damage. Damage values are rounded down, which explains the observed 7.
Disrupters are 50% more susceptible to blast damage, resulting in 15 x 1.5 = 22.5 final damage. Again, the value is rounded down to 22. The blast proc symbol next to the damage value should be the last bit of evidence needed for confirmation.