so, I'll answer everything at once:
1) Yes, there's a lot of macro here, but micro is still present, although not as *intense* as in Warcraft or Starcraft.
2) Attacking from two sides is an old but effective tactic, but I wouldn't spread out the Tau forces too much. Maybe use Crisis Suits to jump around or play with Hammerheads.
Orks and Chaos are all about this: on one side, Sluggas with Mechs/Raptors, on the other, Boyz/Nobz.
3) www.warhammer-forums.ru is the largest Warhammer forum in Russia, covering both Fantasy and 40k, and that says it all.
4) Mandrakes are the melee units of the Tau, the ones in the main building.
5) A skilled Tau harass...
is one of the most devastating things.
...they're called Vespid, or simply "flies."
But this works not only against Necrons; it's a real pain for everyone. After the 1.2 patch, the TK+flies combo became a reality. Because you don't really need a full Barracks anymore, and the Tau Barracks is always the first building.
The scheme is simple. The TK shoots at workers (and with its ability, it can take away three-quarters of the health of an Imperial Guard unit, not to mention Servitors or weak heretics, who are driven to near-death by forced labor), and the flies destroy Genestealers and buildings under construction. Both jump around like crazy, and it's hard to catch either of them. Orks can at least get some help from their buildings, but for the Imperial Guard...
They can do this all day long, while calmly capturing the map and decimating your points with Stealth units.
In general...
Against the Imperial Guard, people haven't come up with anything better than running around in pairs of Tactical Squads + Force Commander, and shooting. You can try to block the TK with Scouts, but they'll just run around. But the flies can ruin everything with their Sonic ability. Yes, the Force Commander also needs to shoot, because it won't catch them and won't hit them even once. You should build Genestealer nests as close as possible to the building, which should be upgraded to a Lictor Nest as soon as possible, so that it can shoot. Then they won't be able to get out from under it without taking losses.
ASMs, despite their jumping and flying, are completely useless. The flies' Sonic ability, the TK's ability, and its flamethrower are all area-of-effect attacks. And if you run them into a mine, you can be sure of the outcome.
Chaos is the same.
Against the Necrons, I don't know; a couple of Necron Warriors and a Necron Lord constantly chasing the TK should ease the pain.
Against the Imperial Guard... there's only one solution: destroy the enemy base yourself with a Command Squad. Kasrkin will hurt them much more than they will hurt you; hide workers with Guards in buildings, and that's it. Upgrade the Lictor Nest. And even the TK and the later-arriving Fire Warriors can be easily tied up in melee by the Guards. They are surprisingly versatile.
Against the Orks, it's relatively easy: again, you run and destroy their base with a Mech...
But it's better to send a separate squad of Sluggas against the TK.
The flies can be dealt with by Nobz while they're trying to save their TK. The main thing, as with the Guards, is to apply strong pressure.
Against the Eldar, it's also difficult, but quite possible.
Engage the TK in melee with Guards, and shoot down the flies with two Shuriken Cannons. It's better not to use the Rangers' "imbad" ability, because the flies are detectors.
Alternatively, build a Fire Support Turret, use its second ability on the TK, and then engage in melee. And it will scatter the flies with its attacks no worse than any Sonic ability.
In a mirror match, I don't know. I don't have much experience with Tau vs. Tau after 1.2; I haven't played them much. But you just need to try to force a fight closer to his base, run the TK away from his flies, and chase his TK away from yours...
In general, mirror matches are boring...
So, that's it. I've written a lot here.
P.S. Other users pretend that they only play Heroes day after day *lol* xD