Well id have to say the scarriest think in your list is probably your Wrathlord, lol who would have guessed. But i think your greatist weakness is in your low number of troops and short range.
Guardians are easy meet for Tau pulse rifles, pt for pt, a ten man team of FW's should kill half the squad in turn one.
The Reapers should not be considered for such a small game, they are a small and an expensive squad. With there low T value, and only 4+ save, even taking some fire form a squad of FW's, from the Taus weekest weapons, str 5, will eat them up, and cause a moral check. With only 3 men, they cant really stand up to 12 shots form a full man FW squad.
The wrath guard are tough, but there weapons only have a 12" range, they will be easily wilted down by a crisis with plasma cannons or fusion blasters. There only chance is trying to go after FW squads, as they will never catch up to anything in a battle suit, and will probably spend most of the game going across the field, just trying to get into shooting range.
As i said your wrathlord is probably the scariest thing you have, and im sure it can hold its own with its SC and high Toughnes, but realize, it will never get a crisis suit into hth, and thus its 10str hth attacks will never be used, and its SC has too short a range to be trulley effective, in the end it probably wont ever make its pts cost back in a short game. However if you put the star cannon on the wrathlord, which has a higher BS then guardians, then you turlly have something your opponint has to worry about, because its tough, it has wounds, it has long range, and the starcannon can easily hunt down crisis suits and broadsides alike.
Im afraid that Iyanden is just the wrong army list to use agians tau.
