The ugly step-sister (well one of) of the Heavy Support choices for Tau, a unit which when you boil it down is actually pretty decent but really compares poorly to the anti-tank potential of Broadsides and Hammerheads in the tank heavy 5th edition. Let's break the unit down to explain this statement more.
Sniper Drone teams are limited to a single choice but up to three separate squads are allowed to be taken within the one choice. Combine this with each Drone having a target lock and this allows the 'unit' to attack up to nine different targets in a single shooting phase. That's not including the extra three networked markerlights the unit contains (three more targets again). This is pretty impressive and has a lot of applicability as suppression fire but this is then limited by the rail rifle on the Drone itself. At S6 AP3 the weapon isn't bad and it certainly has the fire potential to do quite a bit of suppression damage to vehicles but isn't going to do this all that reliably. Even firing each squad at a tank isn't going to reliably net a result and for the points you pay, nine S6 shots isn't that scary to infantry either (though the Markerlights can remove cover).
The advantage of all of this however is that Sniper Drones have a Stealth Field generator which makes them quite resistant to damage at range. First off opponents are going to have a hard time seeing them and since they have guns which out-range the average roll on the 'spotting range,' this is actually useful. Ultimately this only protects the Sniper Drones from ranged firepower and anyone who gets close and can put any decent amount of firepower (i.e. double-tap) will be able to remove the Drones without too much trouble. This durability is again increased by having multiple squads within the unit but they are still very vulnerable to anti-infantry fire from up close.
All of this for 80x3 (240) points and it's not that bad. The unit is significantly over-priced which is a common theme for old books so not a surprise but a unit which actually takes advantage of the Stealth Field generator and has a lot of fire potential against light mech and MSU armies is nice to have (the extra markerlights aren't anything to sneer at either). The big problem comes though when we look at the other Heavy Support options which are much more reliable in terms of anti-tank and ultimately outshine the Sniper Drones in 5th edition for that reason.
So what are potential fixes? Obviously a huge points reduction and I think two USRs would help. As we've discussed in the Drone review, giving Drones the Relentless option would give them a lot more mobility options and in particular let them take more advantage of JSJ and the stealth field generator (thus reducing their weakness to close ranged anti-infantry firepower). The downside of this mobility option would be losing the ability to fire the markerlight but being able to move and fire the heavy weapons is important I believe. The other USR, Stealth, would make them more durable to any firepower that gets through whilst still not really protecting them against close ranged anti-infantry firepower. This would fit well with the Stealth Field generator and give them that extra bit of durability.
From there, and as with many Tau entries, more weapon options are needed. I would continue to use the ranged options in the middle strength area (i.e. Missile Pods) and have a couple of options which are more oriented to anti-tank and anti-infantry, though the Rail Rifle is a nice middle ground. The one issue with the anti-tank guns such as the missile pod, is the ability for suppression fire is very, very high which would need to be balanced by the points cost.
The weapon options whilst also increasing their mobility and survivability would help the Sniper Drone teams compete with the other Heavy Support options in an environment where tanks are very common and important. They will never be the anti-tank options Broadsides are (and shouldn't be), but having some ability as a suppressive device with good ranged defenses would reduce the burden on other options (i.e. Crisis Suits) which allows codex flexibility.
