While I think it’s nice that enemies use grenades. It really gives the player an incentive to not huddle up too much. Pandorans do seem a bit too grenade-happy, however, and certainly have easier access to grenades than the player does (I can barely afford to have 1 grenade per soldier on a mission, as the grenades are very expensive to manufacture). The big issue seems to be, that 1 enemy grenade, more often than not, seems to be enough to destroy your soldiers’ weapon. Place soldiers too close, and not only will they both take damage, but they suddenly become single-use healbots, taking away a big chunk of your damage potential on the mission itself and requiring a fair bit of time in the geoscape to build a new weapon.
I think the damaging and destruction of equipment is a very nice element of the game, but it shouldn’t completely ruin the mission just because an enemy lands 1 grenade (since they seem to have an abundance of these)