Hunting Blade: Two highs make a maximum. Maximum is the cap of damage boosting - Once you get there, you can't deal any more damage than that to that X monster race using that weapon.

A bit more info on this. Let's say we had numbers, instead of low/high/ultra/etc. Low is 1, Medium is 2, High is 3, and so on, with maximum at 6. (and if you didn't catch it - Very High is 4, and Ultra is 5.) That's pretty much how the damage bonuses work. One other thing to note is that even if you get a general damage bonus, it won't add up to a monster race bonus if it already hit the maximum.

Avenger: Yes, damage bonuses stack with type advantages. (If that's what you meant? Because Avenger's fiend bonus was removed quite some time ago)

Vog Cub: It doesn't give FULL fire resist - The actual cap of resist is two whole meters. (in numbers, it would be 140, a full meter being 70, and each Vog piece being 35) However, fire resist variants are kind of useless, since to hit the cap you NEED a fire resist shield, unless you get high/very high/ultra/maximum fire resist variants on a five star armor with natural fire resist, plus fire resist trinkets. So in the end, you'd hit such cap no matter what, and the variant would be pretty much a waste.

Though this is more of a flaw on the current status resistances system. (It annoys me - having 280/four full meters of resist, which is the most possible to obtain, is the same as 140/two meters. And that doens't give complete immunity - Not even "amazing" resist, just "great" resist.)

Also remember what Aeca said about checking your character info - You can get most information on bonuses there. Although status resists only show up to 70 resist, and your shield's resist won't show. Kind of silly.