it really depends on how you like to play.
i just finished a tankish tau force(1850). it is extremely small for tau, but then again it is focued on the devilfish and hammerheads. being forced to take the +1crisis suit hurt me some on my original idea.
if your going to play this there are a couple things to remember-skimmers in 40K are very survivable especially if you give them the neccesay upgrades and remember to always move over 6" per turn. the key here is that all your serpents are not scoring units, but the guys inside are. the key thing is to keep them out of close combat, reducing them by 50%+, getting pinned or running off the table.....to do this the best way id to keep them inside thier vehicles as much as possible. this has a couple pro's and cons. doing this reduces the number of shots you have each turn, if the vehicle is destroyed your opponant gets to re-roll for wounds on units traveling in fast vehicles and they are effectively stuck/pinned in the reckage for the next turn. on the other side you avoid all the stuff mentioned previously and you get instant 4+ cover saves from the wreckage for anybody that survives.
i thought about doing what you did with eldar but i liked the tau a bit better for it, especialy since i can upgrade the vehicles BS
i also play ravenwing and in armys that have light skimmers like land speeders and vipers i tend to run them in squads for increased firepower and survivability.
in the end it is highly likely that your army can in 6 turns do enough damage to your opponant to win the game through attrition since he is less likely to be hurting your scoring units while you are plucking away at his.
i love mobile armies, proxy with some friends to try it out and see how you like it.
as long as it is alegal list and you enjoy playing it thats all that really matters.
