Yeah, Rangers can be a pain, better almost to just run around till T2 Pathfinders come out. Which doesn't take to long if you eco boom correctly.
Think about it this way, if you didn't need Vespids, you'd have enough req to make another FW squad and build either a Gen or LP, which would give you better firepower early on and better econ (cheapest/quickest cappers) which would make Tau totally PWN Tier 1. So they intended for you to get a weak expensive unit early on to handicap Tau from a booming econ/army.
This is a risky techy BO, but if you can keep your builder units alive you'll have massive firepower very quick. 2 builders to Barracks, then 2 gens, and 1 FW squad to harrass and lead enemy away (skip TC and Vespids), you can make the Path building ASAP and get your Pathfinders and Broadsides very quick. I'd rather take the risk and end up in T2 w/ a good econ, as opposed to wasting req on Vespids and cripple your econ.