Not a rules issue, but a team that overused HE grenades would end up with a reputation in my games. That kind of major havok is the kind of thing that steers employers away from a team unless they're hiring for maximum disruption jobs. Likewise I doubt that many corporate security teams would use grenades as they would tend to damage the facility.
One of my major beefs with some of the earlier SR systems was that grenades simply weren't lethal enough.
I think grenades have become too lethal, or at least undodgeable wireless grenades are.
If I had to sum up my "crunch" problems with grenades it would be with the following piece of math.
HE grenades do 16P-2AP.
If a force six mage casts a fireball spell at force six, and somehow gets six nets hits (no hits to dodge at all from his target) then he does 12 P-6AP.
With every 3 AP being roughly equivalent being to another DV that's about 14P.. (The only time doing huge armor decreases is better than doing moderately more damage is if they're spending edge to soak and if they're doing that then you're once again winning by default)
A force seven mage casts a fireball spell at force seven and somehow gets seven net hits that is 14 P-7AP
That is equivalent to roughly around 16P -1AP..
Granted, the spread on grenades will make them a little bit worse for AOEing a group that is far apart, but I don't have the book in front of me to look at if magic AOE spells have a fall off rate and if so what is it.
If you do not want to overcast and risk coughing up a lung a mage has to get to magic 8 before he can cast a spell which is a better AOE than a rigger with an Ares Alpha firing HE grenades.
Also that mage needs a magic pool of 18 dice to get six hits just on average, and 21 to get seven, 24 to get eight. A rigger can reliably get the three hits he needs to make his wireless grenades land on target with just 15 dice. (3 Agility, 6 Heavy Weapons, Specilizations Grenade Launcher, Wireless mode enabled on the Ares Alpha, and a reflex recorder for heavy weapons).
If grenades are AOEing better and take less effort than magic AOE.... I think they've become too strong.