I don't have good answers to all of it, but some things to keep in mind...
- You get up to 5 IP and your Initiative up to (Response + INT +8 )
One of those IP is eaten by "controlling the vehicle" (drones being a sub-set of vehicles), pg 168 & 169 SR4A.
- VR lowers the threshold of tests by 1
where's that rule coming from? I'm not finding it.
- You can perform every Combat Skill with Gunnery, from Unarmed to Laser Weapons (only one single skill is needed) or you use your own skill (like suggested in Cyborg rules) but with the "Jumped in" Attribute (i.e. Response)
Actually, it's Gunnery + Sensor (SR4A, pg 247), not as easy to cheese out as Response is.
You did leave out one big cheese of drones: no recoil unless GM imposed.
As for countering drones:
{u]Jammers[/u]- A good facility's going to have them, Probably rating 5+ in many cases. These don't just affect your drone's Signal, they also affect its Sensors (Drone Sensors are Signal rating 4, I'm sure there are ways to raise that, but I haven't seen them).
Matrix Security- If you don't slave the drone (stupid call, I know), they can hack in as normal, and delete your account or shut the drone down at their leisure. If you did slave the drone, then when they attempt to access the drone, the drone forwards them
to the node your persona is running on (Unwired, pg 55). Now, if you're not a technomancer (and if the spider's a 'mancer, even if you are), they can hack into your home-node. If they're stealthy about it, they can be inside and get your GPS data, send in a HRT team and then crash your commlink. Now you and your drone are hosed. Before you say "hidden node", I've found that that just slows them down, and not by much if they see a drone.
AV Rounds- -6 to your drone's armor makes your day pretty lousy. Smart armor works a maximum of 10 times (unless the drone comes with higher smart armor, the limit is 10, Arsenal, 132-133) before you've lost your 20,000 nuyen investment.
magnets- Really big ones.
For every hack, there is a counter-hack. Are drones balanced? No. Should they be? Not in my opinion, that's the fun of Shadowrun, you can't just go bullet-to-bullet or bullet-to-spell. If you run into a beast (and it might be a sammy with just the right combo of stuff to shut your team down as a drone or mage), you need to get smart, not get bigger guns. Balanced games simply turn into a race to higher modifiers (look at DnD4e), unbalanced games are a race to higher IQs. Why worry that you have such high armor when I can force a confrontation at a social event where armor is not allowed? Or a dark alley where I've had time to rig a vat of acid overhead?