I would not like not consider miltank a true nor good counter...It doesnt have a good special defense nor can it be EVed to outspeed moltres without being specially defensive which wouldnt really be good except for countering only moltres and he only has thick fat to stop fire blast....here's a good miltank countering moltres set
Miltank @ Leftovers
Thick Fat
252 HP 82 SpDef 176 Speed
Timid
Rock Slide
Body Slam
Milk Drink
Heal Bell
Those are enough speed EVs to outrun positive speed Moltres.... and timid moltres does about 44%-56% with a LO air slash... this is probably the only set miltank can run to 100% counter moltres at full at health...still a very shaky counter to say....
Miltank @ Leftovers
Thick Fat
252 HP 82 SpDef 176 Speed
Timid
Rock Slide
Body Slam
Milk Drink
Heal Bell
Those are enough speed EVs to outrun positive speed Moltres.... and timid moltres does about 44%-56% with a LO air slash... this is probably the only set miltank can run to 100% counter moltres at full at health...still a very shaky counter to say....