Sounds like my strat:
http://www.battleforums.com/showthread.php?t=99322
The time to use mine is when you need speed as much as you can. This is if it's a close map or if they already see you building temples.
I wouldn't wait until tier 3 to attack, but rather, if the map was big enough, I'd throw down 2 temples and a house, make 4-5 necs with their ups, 1 wagon, 2 stats and commence the attack.
For all of our strategies, make sure you bring sacrificial skulls as it gives bonus health regeneration, in addition to statues.