You don't have perfect accuracy, jitspoe added the player direction and speed to paintball in 1.72. Basically this means that if you are moving 50units/second towards 90° and fire a shot at 180° at the speed of the gun(I believe the cocker is approx 1320units/s) which you are using, the 50units/s at 90° get added onto that ball and it will curve accordingly. It's hard to notice that anymore since it's been in play for a while, but when it first came out it was really noticeable.
As for on-impact grenades, they are way too deadly. "Default" settings are set at 1 grenade per team, which seems reasonable, but when you take into account that a new one spawns 30s after a previous was picked up then you end up with too many in play. Since grenades don't automatically "return home" like guns and ammo, then perhaps you should make grenades only spawn after they've been used, to ensure that there are only 1*Teams maximum in play at one time. I also wouldn't mind to see them respawn after 60s like the guns, but if the other team managed to pickup a grenade that came from other team's spawn, don't spawn a grenade in the other team's spawn until their opponents use it.
Unfortunately the way that the grenades are now offer very little depth to any decent gameplay what so ever. If I hear a grenade being tossed from the other team, I usually hold off on my rush, unless I can see the smoke, then I continue. If I see a grenade land near me then my first instinct is to move out of it's blast radius, which either: removes my cover or gives away the position of my teammates and I. With knowledge of angles, speed and practice you can make some nice bounce-tosses on unexpected opponents to get them to move out into open(sandtrap is a favorite of mine for this). Impact grenades simply clear out entire teams in one shot and there is no chance to avoid them.
Power vs. Luck
Luck in terms of the autococker if pretty small compared to the grenades. Typically with guns you shoot when you are capable of seeing an opponent or you are spraying an entrance or area in which you know an opponent will be passing through. With that said, spray isn't luck. Spray isn't completely unavoidable, with experience you know where spray occurs and you can identify it from far away. The only luck surrounding spray is when an opponent runs through it once, or numerous times. It may be bad luck for the opponent that "falls into" as result of him mis-jumping but that doesn't really apply to the gun being considered lucky.
Non-Impact grenades typically have a mind of their own, the newer style ones(post-1.72?) no longer have fixed speed, as the speed of the players are also added to the grenades. This causes variations in path and bounces of the grenades and from time to time you will get a ban bounce that will be enough to eliminate you. These grenades however serve more purpose for strategic tools and are only deadly when then luckily strike a near-by teammate.
Impact grenades however offer no warning for arrival. Before you can react to one, it has already landed 3 feet from you and has killed two of your teammates. The only chance you have with an incoming one is that it hopefully lands behind you so the payload -hopefully- doesn't effect you. These grenades are more effective on the smaller maps because it doesn't take a genius to determine where the other team is going to be. On arctic if you launch one into the ice during the round chances are you will hit at least 1-2 unless the other team is camping the flag or in their tower.
Just my perspective and some ideas, feel free to contact me by email or on IRC about anything.
-XtremeBain