From: Lower Saxony Germany
Field you could always build a mech unit towing AT guns to keep up with your armour.
AT is a defensive weapon if I am correct, your armour is offensive. So they will not really work together. But having your armour and mech units in the same hex then if your armour gets attacked , your AT boys will be there to help out.
Pulling back a few hexes is also a possibility, armour pulling behind a defensive line of AT and MG will really cause havoc on the advancing enemy. It should be reduced so much that your armour can punch a hole through the weakened line and if possible make a pocket or cut of his supply lines.
By pulling your armour back and resting, you can build up supplies in oil, ready for the offensive. Always keep an eye on the oil gauge. Never run out of it. Otherwise your armour is toast.
If possible get your engineers out in the field and upgrade your raw and oil.
"It is not enough to expect a man to pay for the best, you must also give him what he pays for." Alfred Dunhill