In this post, I will share a bunch of tips I learnt from some experienced Crota raiders when doing this week's hard runs with them. Some of them might already be shared somewhere in this forum, in that case I apologize in advance:
1) Most important tip: how to have everybody in the fireteam to all have more than plenty of heavy ammo for Crota fight, using the heavy ammo glitch;
Step 1: choose a primary with small mag size. Word of Crota / Fatebringer work nicely. Say the mag size = X;
Step 2: Reduce your total primary ammo to exactly 3X (e.g.: Fatebringer has 13 bullet per mag, so reduce total ammo to 39);
Step 3: Empty your heavy ammo;
Step 4: Equip special slot with Ice Breaker (make sure Mulligan is unlocked and selected);
Step 5: Enter the crystal circle when you completed the 4 steps above;
Step 6: After the entire fireteam enter the circle, the shield should appear, so are the enemies. Immediately empty your primary weapon as fast as possible;
Step 7: Switch to Ice Breaker and kill Acolytes. They will drop heavy ammo all over the place for you, usually enough for the entire Crota fight;
By doing this: you will be free of heavy ammo concerns for the vast majority of the time.
2) Forest: tips for surviving the bridge building
After getting through the lamps and triggering the bridge to build, the goal here is not necessarily to kill the Orge (which can be very difficult if you don't have GJallarhorn with lots of ammo), but to survive long enough until the bridge is fully formed.
Basic moves for all classes: jump onto the rocks so Thralls can't hit you.
Once Orge appears and sees you:
a) Hunter tips: use all of you cloak abilities (crouch first, then blink strike, then bladedance) + hiding behind rocks + Don't Touch Me. You should be invisible for the entire duration;
b) Titan tips: stun Orge with Sniper Rifle as long as you can, then jump off the rock and look for hidden spots, then as the last resort deploy your bubble, preferably blinding ones from Saint-14;
c) Warlock tips: stay alive as much as you can, then use Fireborn to buy more time;
3) Bridge Crossing
The goal here is to a) get one player cross the bridge, and b) have players alive on the entry side of the bridge to snipe at enemies after "somehow" trick the game to think that nobody on this side are still alive (the cue to know when the game is tricked is when all the adds on this side of the bridge are despawned), c) "cloaked" as much as possible in dangerous zones;
With this method, the crossed player should just stay alive, and rely on his teammates on the other side to kill everything;
To do a):
method 1: normal crossing by having 2 players guarding the totem pole;
method 2: "sword swim", "fly" across the gap by repeatedly pressing melee button; (specific route has to be used. See YouTube for details)
To do b):
The players stay on the entry side can
i) jump up to the tip of the high tower (specific routes for different classes has to be used, see YouTube for details), which is considered out of bounds by the game and therefore ignored, or
ii) Sunsinger with fireborn can commit suicide, wait for adds to despawn, then self revive, or
iii) just commit suicide and watch your friends carry you
Regarding the sequence of a) and b):
If nobody on the tower side needs to rely on Sunsinger fireborn, then the sequence can be b) followed by a). Get everybody up to the tower tip, wait for all adds to respawn, then send 1 player across;
4) Bladedancer sword holder moves during Crota fight (Using the middle ledge strategy)
The goal here is to get sword 3 times and hit Crota 6 times, with 3 slams each time (if missing 1 in one hit, then need to do a 4-slam hit to make up).
After cleaning up the crystal room, make sure your super is charged (teammates should drop enough orbs to get you this):
Step 1: move with everybody to the middle ledge;
Step 2: kill sword bearer (sword holder should just unleash all of his heavy ammo on sword keeper, because he does not need hit Crota with heavy);
Step 3: Immediately jump off the ledge, activate super mid air, and RT to go invisible as soon as you hit the ground;
Step 4: Run to the sword, hit RT to go invisible again, then pick up the sword; (Note: you have 15 seconds to complete step 3 & 4, so take your time to do it perfectly);
Step 5: Get close to Crota. When you are one jump away from him, instruct your teammates to fire at him to get him kneel down right when you are near him);
Step 6: Hit him with 3 slams, drop sword, blink strike him to become invisible, then pick up the sword;
Step 7: Immediately after your teammates kneel him, hit him again with 3 slams (if you can only get 2 in from step 6, then go with 4 slams);
Step 8: Run back to the Crystal room (use invisibility as much as possible to minimize the risk of getting hit by boomers);
Step 9 - 15: repeat step 1-7 above for the second sword run;
Step 16: Run into the Orge room and jump to a ledge (use invisibility as much as possible);
Step 17: Kill orges with teammates and pick up orbs to recover health and recharge super;
Step 18: Run into Crystal room (use invisibility as much as possible);
Step 19 - 25: repeat step 1-7 for the third sword run;
Useful stats:
a) 18 slams are needed to kill Crota;
b) Crota will become enraged on hard mode after 15 slams (but we have observed him becoming enraged after 14 slams a few times);
Therefore, the goal is to get >=12 and < 15 (maybe < 14) before Orge fight (step 16);
4) Tips for teammates of sword holder during Crota fight
a) See section 1) above for heavy ammo glitch;
b) Titans should use bubbles at the following times: a) initial fight in the crystal room (right before the shields disappear, the best cue is to drop bubble as soon as the Radar appears), b) come back to the crystal room after a sword run; c) move to the middle ledge from crystal room for 2nd and 3rd sword run, d) Inside Orge room;
c) Warlocks should focus on making as many orbs as possible by killing the 4 knights during the initial fight in the crystal room;
d) Pick up your armor piercing sniper rifle if you have one (Vanguard offers a LDR 5001 that does this), so you can shoot at sword bearer through rock walls that he likes to hide behind. Note that you can do the same amount of damage, the walls you shoot through won't reduce any of the damage!
e) During the Orge room fight, jump onto a ledge when you enter the room;
f) When shooting at Orges with rockets, make absolutely sure that no teammates will step in front of you;
g) Don't step in front your teammates at any time;
i) During the third run after Crota enrages: once you kneeled him for the second time, move away from the "barrier" window so you don't get murdered by thralls who can claw through the barrier;