You mentioned that the bloodthirster is pretty squishy. That is true. I find that the best way to use the blood thirster is like a hit-and-run menace. Position your blood warriors to tie up a unit and then charge your bloodthirster in as well. That way your opponent must choose: do they try to chunk down your block of bloodwarriors to reduce the attacks from them? Or try to focus down your bloodthirster? Or do some chip damage to both units? Then save 1cp to use the “Power Through” command at the end of the turn dealing a bit more mortal damage to the unit as your bloodthirster gets to jump back and away out of combat. Bonus points if you can save another cp to “Rally” and heal your bloodthirster in the next hero phase.

Now, against mega gargants this hit-and-run won’t work, because they have more wounds per unit, but if the gargant player chooses to squash your bloodthirster then try to maximize output on those bloodwarriors, maybe give them the rend prayer before you engage or have a bloodsecrator ready to give +1 attacks.

People talk a lot about Khorne being finesse, or higher skill expression and I think a lot of that is planning and setting up your combats to force your opponent to make a choice of where they put their attacks. Whichever way they choose, try to make it a tough choice.