Undivided & DeathGuard vs Tau  - I used the list below, and the DeathGuard was lord w/ plaguebringer; 10 chosen w/ 2 meltas, 2 plasmas, 1 flamer; dread w/ ccw & missiles; 4x 7 plague marines w/ plasma, melta, fist/plasma AC. Tau was naturally a lot of shooty death: shas'o + friends; 3x 3 deep strike crisis (plasma/fusion x2, plasma/flamer x1); 3x 12 fire warriors w/ markers; 2x 6 vespid; 2x 8 pathfinders w/ warfish; railhead; skyray; 3x sniper teams; 3x single slot broadsides w/ shield gen & shield drone. We decided later he shouldn't have deployed them all seperately, as 5 heavy slots is one thing but 7 is another all together!
Tau Deployment (Chaos L to R):
Warfish, pathfinders (woods), fire warriors (woods), fire warriors (behind woods), broadside (hill), sniper team (hill), hammerhead (pointing at defiler), crisis HQ (behind hill), broadside, sniper team (rocks), pathfinders (rocks), warfish, broadside, sniper team (building, 3rd floor), skyray (building, just 6" in), fire warriors (building, 4" in).
Chaos Deployment (Chaos L to R):
Plague marines + lord (left building, over 6" in), havoks (building, 4th floor), defiler (half behind building), 1k Sons (behind rocks), DG dread, plague marines (woods), fist CSM (behind woods), chosen (infiltrated into woods mid-table), plague marines (right building, left edge), shooty CSM (building, over 6" in), noise marines (building, 2nd floor), plague marines (building, right edge), obliterator (behind building), Undivided dread (right of building).
Basically a lot of Tau guns pointed at a building with 2 squads, an area of woods with a few squads and a building loaded with chaos. First turn to Tau.
Tau Turn 1 - Defiler is immobilized, plague dread is railed, undivided dread shrugs off the skyray, and the chosen take a blistering amount of firepower, dropping the five armed with bolters.
Chaos Turn 1 - Plague marines advance a little, though without leaving their terrain pieces. Deathscreamer lord joins the plaguers in the center woods. 1k Sons move into the rocks in front of them, shooty CSM move within 6" of their building's edge, noise marines do likewise to bring the blastmaster into LOS and the undivided dread rages forward a total 8". Havoks stun the hammerhead, defiler scatters and takes out 1 sniper drone, chosen knock the shield drone and 1 wound off a broadside, and plaguers and deathscreamer lord can't scratch a second broadside, despite a 6 for the demon cannon's shots.
Tau Turn 2 - 3 crisis w/ plasma + fusion strike near the defiler and explode it. Assorted fire drops a couple 1k Sons in the rocks and the skyray immobilizes the undivided dread. The chosen are shot down to a single plasma gunner, who keeps his cool. Vespid zip up and bother the 1k Sons and the plague marines, dropping 1 plaguer. 1 unit assaults the 1k Sons in the rocks, but only the sorcerer can take anybody down.
Chaos Turn 2 - Plague lord + marines push across the havok's building and assault the struck suits, trashing them and consolidating into the 1k Son rocks. The fisty CSM mobilize and help the Sons out with the vespid, crushing them for the loss of 1 more Son. They consolidate into the rocks too, making that 3 squads & 1 lord all loaded into 4" x 7" of terrain. Other plaguers with deathscreamer lord hop to the chosen wood, then turn and vaporize the unengaged vespid squad (6 for demon cannon again). Plague marines in other building push to the edge, and chaos fire drops various fire warriors in the other building. The havoks also pound the hammerhead again, removing the railgun.
Tau Turn 3 - 3 crisis w/ plasma + fusion strike near the forward plague woods, and combined with 3/4 of the Tau army are able to take all 6 plague marines down. The lone chosen is killed, and the deathscreamer takes 1 wound from something. The rest of the Tau manage to trash the fisty CSM squad to 5 models, and the 1k Sons are now at 2.
Chaos Turn 3 - Retaliatory fire (1 shot of which was from the dread plasma cannon) kills 2 struck crisis suits, and sends the survivor fleeing several inches. Far right plague marines advance for the fire warrior's building, and lord + plague marines continue heading laterally to the right, staying behind LOS-blocking terrain. Fisty CSM likewise pull out behind the rocks, but the 1k Sons play it ballsy and scoot towards the Tau and their guns. Bolt of Change misses, naturally. Right noise / CSM bunker pins the fire warrriors across from them with blastmaster and other fire. Deathscreamer ignores the crisis suits in front of it to make a break for the pathfinders in the rocks ahead of him. He makes both sets of difficult terrain rolls and hits combat, rolling 4 for the demon weapon. 8 attaks later all the pathfinders are vaporized. The lord consolidates into the fleeing crisis suit, but it fails to rally and flees further away, leaving the lord facing a warhead, broadside and 5 sniper drones ...
Tau Turn 4 - 3 crisis w/ plasma + flamer strike near the havoks, and scorch 4 marines. Other Tau shooting wastes the 1k Son remnants and fries the stranded deathscreamer.
Choas Turn 4 - Fisty CSM squad 2x flamers the crisis suits and then fists them to death. Plague lord continues moving to the right. Forward plague marines advance to charge the fire warriors in the opposite building, but the aliens are all shot down. A broadside or two loses a shield drone. The oblit finishes what the chosen started and zaps the broadside who killed the 'screamer.
Tau Turn 5 - Shooting is largely ineffective against plague marines, and the obliterator is railed in return.
Chaos Turn 5 - Plague marines push into the building across the way, and do nothing to the skyray still parked there (but long out of seekers).
Game is called, as a party has to be gone to. With a margin of less than 300 points, it's a ... DRAW
Building: APOC Reinforcements