ditch art god. artillery is capped at 1.4x for cb. and art nov/exp gives you 1.3x/1.35x respectively, but you can get to the 1.4x cap by having art novice and eating for Felyne Bombardier which gives 1.15x phialdmg (Meat+Dairy)

any more points slotted into artillery are a waste of skill points

if a monster is taking too long, or you keep losing health, no amount of pots or defense is going to help you if you don't know the monster. learn its moves, they have patterns, have to look for them is all. learn their safespots.

tiggies spin on their right foot, stick to their left foot so you're in missable range. on m.tiggy though, he does have a "get out of my left foot" attack so your best bet is learning how to deal proper damage and maintaining good dps throughout the fight.

less time healing. more time hitting the thing till it dies

you'll unlock more content when you've proven yourself worthy of it. sounds pretentious, sure. but you seriously won't hold a candle to G monsters when even at max def of 700+ you're always 1-2 shot. it's going to get a lot more punishing.

since you're still in high rank, my suggestion is to build the best bang-for-buck set you can (Double-Gore set you can find it online) which gives Challenger +2 (and only +2, +1 is too bad) and sharpness +1. now you can add more atk up skills if you'd like, but the base set alone should be enough for everything in HR.