Ok, what u stated mostly here it is about perfect attack type in some cases.
Of course u must be careful every time at your units attack type and armor type, like u said footman vs archer (melee vs medium armor+ perfect damage), or gryphon vs bear (magic attack vs heavy armor=perfect damage), about the breaker vs the bear, it is not recomended because the feedback of the breaker will not stand against the huge damage of the bear (the breaker has medium armor and the bear melee attack).
Mass huntress strategy is used usually in 2v2 games, and is rarely used in 1v1 and even more rarely against human, u see rifle vs hunt has perfect damage, and hunt vs rifle is also perfect damage, like u said a few footman in front will be good.
About the giant and bear mass strategy, this is almost impossible to achieve, because the mg is trained from the same building(tree) as the bear, and iti takes a while, to get ready bears + mountain giants. So don't be scared about the giant, just be carreful about taunt, and against the bears don't try too much to go to gryphon very fast, just a few knights (not necessarily with full upgrades, let's say lvl2 attack and lvl 2 armor) and rifle and priests some breakers( breakers in the back of the knights, not in direct fight with the bear).
Don't count too much on mortar against units like talon or huntress, some simple piercing attack will do the joob, against talon some dispelling means are also required.