maybe i just need to git gud and that's probaly the case but i want to rant about The Black Shrine a bit;
i get the idea of what they were trying to do i really do BUT after wiping for 2-3 hours on some C-6 bosses i'm pretty done with this.

the idea of C-1 trough 5 (maybe 4) are for you to learn the boss and the patterns and mechanics but the game doesn't do this AT ALL, the bosses die within 2 minutes more or less on lower C's , i feel the real boss begins at C-5 ok that's fine i get it , lets just talk about 1 boss here because i WAS dedicated to beating atleast one of these bastards on C-7 , now i personally think Songakshi is the best designed boss out of all of them and that says alot about the other bosses.

Songakshi now i actually enjoyed learning the patterns and avoiding her frontside but suddenly on C-6 you're hit with a 'clone' mechanic as some may know and at first i was like wtf do i do now great i hit the wrong one and i died and have to restart the boss again, she can also straight up 1-shot you trough FG with that nasty 3 line attack, or that 1 big line , if you plan your stationary SA skills or FG skills wrong you straight up die , im ok with 1-shot mechanics but do these bosses really need several? 
now i have to look up a guide on what the f*ck is actually going on SO counterintuitive. but i managed to kill her with some luck and frantically running around picking up HP orbs.

C-7 everything kills you always everywhere. its unfun, Props to the people who can do it like i said maybe i need to gitgud

in the end i always felt like it was a cheesy mechanic or some poor design that insta-killed me 8/10 times, rarely was it because i felt i played bad or didn't dodge the right attack bla bla i got her to like 10% which was my best try but i can't just can't kill her , i gave up 

TLDR; do black shrine bosses really need several 1-hit KO mechanics? i get that they're trying to make it hard but this is just bad design

Like everything else in BDO, based on RNG and RNG only, you can get easy patern where boss will basically do nothing and die, or you can suffer because boss doing crazy stuff and 1 shot you out of blue.

yes, it was lazy rushed content, quantity over quality.

How's your gear?

Try c7 golden pig. Its the most enjoyable from all the bosses. There are no random sht mechanics and all his attacks are telegraphed.

You describe modern BDO here. I don't remember when we last got actually finished and balanced content

Not to mention how insanely delayed some of the bosses attacks are compared to their visuals. Makes higher difficulties were dodging attacks is important feel bad to fight.

i have 297 ap 308 aap and 396 DP , but i don't think gear should even play a role in something like Boss Blitz , bosses should scale with ur gear because how else then would the ranking system be fair? i just don't get BDO sometimes

Gear doesn't play a major role unless you're really competing for rank 1, in which case the extra few percent might matter.

What does matter is max hp, which admittedly is in part gear, but it's also crystals, adventure logs, and buffs.

The other thing that makes a huge difference is hp on hit. Running grim reaper & draining elixirs alongside hp regeneration skill add ons (and draining crystals if you really wanna min max) make things a lot easier. With sufficient hp pool and regeneration you can facetank many attacks on c7.

Basically, if you're getting one shot by normal attacks, work on hp. If you're getting 2 shot, stack more regeneration.

And learn your pve iframes, every class has them but unlike the pvp ones there's no icon. If you know these it's also much easier.

When attempting C6 and C7, you will need to optimize and min/max a bit.  It's something most people don't do naturally, unless you already do Node Wars.  Like already mentioned above, you want to stack HP because it's not capped and more HP will allow you to soak more attacks when you make mistakes, making the fights more forgiving.  You can stack hp via artifacts & lightstones, you can stack more hp via crystals, and you can gain more hp via food & elixir buffs.  You will be doing a lot of back attacks on these bosses if you're playing the mechanics right, so stack +back attack damage crystals and addons will help.

Def know which attacks siphon hp, and you can add more +hp on attacks via addons.  This really helps because it's not always ideal to run for the health bubbles as that could put you in vulnerable situations.

Try Sangoon & Golden Pig King on C6, they're two of the easiest bosses.  You mostly just have to iframe and stay behind them, and learn a couple of mechanics that's all.  Imoogi is also easy once you learn the mechanics, they've dumbed the fight down by quite a bit.  So watch some vids and you should be fine there.  If you want to attempt C7, don't go in without full elixir rotation and min/max, even some of the best geared people go in with full buffs.  C7 isn't meant to be easy, although they can be once you've got it all down.

I will say though classes are not created equal, some classes simply have a better time against certain bosses.  But that's what tags are for, you can tag a class that's better at doing something your main can't do well.  Good luck you got dis!