Welcome to Librarium Online!
I'm a newbie to the forums but i thought I'd try and start a discussion.
It seems to me that I've been seeing a preponderance of transport heavy armies now that 5th edition has such a reliance on Troop choices. I have been contemplating a list that goes heavy on Marker lights (SkyRay, 2xPathfinders, Marker Drones) and pinning weapons (Fire warriors with Carbines, Gun Drones, Sniper Teams, Rail rifles) and then using XV8's as Deathrains and Fusion Blaster+Flamer teams (Don't know what these guys are called), and Heatwaves.
The idea is to "pop" the Transports (Deep striking could be an option) and Burn the Squad up while pinning down squads that could intervene if the squad isn't obliterated the turn their transport pops. Also could pin squads that proved tough enough to withstand the first round of fire after they get blown out of their transport, to stop them from assaulting the XV8's.
Marker lights would primarily be used to try and ensure failed leadership tests, as well as BS upgrades, and cover negation as needed.
Inevitably their will be issues with this strategy (Ork Horde certainly comes to mind) but surprise could be on your side when you show up to a match with no rail guns and your opponent looks at you quizzically.
Any thoughts on how this tactic could work in a 1500-2250 game? Pro's and Con's? Any discussion would be helpful as I like to try and do things different from what you see most people do...i.e. Hammerheads, Broadsides and Fire Knives.
As an aside: I have learned so much since I started reading this forum in January. I need to give special props to rikimaru, although I don't always agree with you, your posts are insightful, well supported and well written and they have helped a ton. Can't wait to become more involved on the forum.
Don't go too overboard with reliance on Pinning. High leadership values, Fearlessness and so on makes it quite hard to pin units nowadays. Also, tying up Markerlight hits to lower Leadership on the off chance that the enemy unit will fail a save from a Pinning weapon means that you could be losing out on using those MLs a little more productively.
Don't get me wrong. I have tried to pin enemy units from time to time, but experience has led me to believe that for me it is a bit of a wasted effort. I prefer to load up on Pulse Rifles which have both range and firepower, and I only tend to field Gun Drones as "passengers" on the Devilfish I use since they come free, so to speak. I have not yet used Sniper Drone Teams, but I do have a triple-whammy unit awaiting the paint brush!
It is nice to try to find a different style of army list from the more ubiquitous spam which you mentioned (although I hold my hand up as an exponent of such spam!). However, chancing your arm at being able to pin stuff in order to prevent it advancing on you is very risky and could end up with you having a large army in your front garden simply because you lacked the extra firepower that rapid fire weapons would have provided.
All the above is just my opinion, of course. I have my own favoured playstyle which does not include much pinning-capable equipment.
"Tau Commandment #226: Participants who use Velocity Trackers in the Tau Clay Pigeon Tournament will be disqualified"