From where I sit, unfortunately the GDs have sort of slipped through the cracks of development since they were reduced to standard infantry. One or two folks pushed for the expendable/disposable rule gone and so the GDs became very blah.
No one seems to take them any more as they don't really provide anything of real value. Even their speed isn't that great now to be honest. Even without playtesting it's a bit obvious that they're not really worth their inclusion except to bulk a formation, which can usually be done with other options that are more useful. I've stopped using them entirely now - which is annoying as I have them just sitting in my Tau box taunting me ÂÂ
Personally I'd like to see them as:
Inf 30cm 5+ 6+ 6+ with Pulse carbines 15cm AP5+ Disrupt, Expendable/disposable/grot etc(but not for formation - mentioned in the data sheet)and purchasable as a 4 or 6 unit formation for 125 or 150; or a 2 unit (or 4 unit?) upgrade for certain formations priced at 25 (or 50 points respectively). Another 25 point upgrade for the list would be very handy IMO. I don't know about others but I often find myself with 25 points left over and there's only the Bonded Team option available. If you've maxed your FWs out on upgrades you're behind the 8-ball in points. Plus with just 2 units as expendable etc it wouldn't be too ablative in terms of BMs as you'd only soak 2 BMs.
I'd also remove the Tau Jet Pack rule because it detracts from their value in speed (because the extra 10cm move for TJPs means their speed needs to be reduced a tad) and let them keep up with armour.
A 30cm Infantry formation would also fill an original niche for the list.
I think it'd be nice to see an iconic Tau unit back in people's list.