Solo. Never coop with randoms, for sure everyone will die many times.
It's either solo, or hunt with really good friends you know is good at the game.

Before that...go follow kirin's footprints (don't hit kirin) to unlock more tempered elder dragon investigations, unlock at least 8 of them to be safe.

Here's my tip, bring thunder proof mantle and vitality or rocksteady..if you play melee best is to hit 1-2 times on the head and run, repeat. Remember don't rush...if there are two lines of thunder about to hit you and you have nowhere to run, try to run towards kirin and stay beside lol.
I play insect glaive most of the time so sometimes I will jump straight to it's head and hit it.

i just got the Warrior Streamstone after completing a Tier 2 (HR30+) tempered monster quest.  i was at HR54 and turned HR55 after the quest.  visit the Smithy and he will unlock Augment Equipment option thereafter

as mentioned by other reply, Hero Streamstone is from Tier 3 (HR50+) tempered quests. they are tempered elder dragons

if someone join you without you sending SOS, that someone is from your squad...
Moral of the stoli, select 1player from the quest selection, if you want to go solo.

did u joined random session? there is possibility that he joined your quest through same session.

like the rest said, put restriction to 1 player only.

or, like i always did, SOSed, if they died one time, can be he died by unavoidable circumstances for example stun and nobody near him trying to help him.
After that i will inspect their equipment first, if died again, will kick from quest. heheeh

do you have equipped stun resist charms or decorations? just 3 levels.
my suggestion to hit nergigante must equipped with lv3 stun resist + earplugs lv5

nergigante is roaring so much, you must get prepared yourself with earplugs lv5. Just go to check which kind of armors have earplugs skills or add up the decorations into the empty slots.

Another tips is when nergigante go to the area when you first go down from camp 1. There have many rock on the ground, you can pick some rock before you proceed to hit nergigante. In that area, you can see many pillars on the above there. Some pillars can hit down by throwing a rock. You can pick up the rock to hit the pillars when it stand below there. 900+ damage per pillar hit.

This is the tips to save time, later in HR15. You can use the same method to hit xeno'jiiva too. There have a rock beside the camp. Just pick up the rocks before you proceed to kill that xeno'jiiva. Just hit the pillars above when xeno'jiiva stand below there. 1000+ hit per pillars, there have around 2 pillars are shoot able.

looking for players HR 50 above that don't sell out easily while fighting tempered elder dragons and farm brigade armour XDXDXD

how to jump to HR32 directly without complete the HR29 to kill two tempered Bazelgeuse main quest?

IMO, if you're still experimenting with new weapon/armor, don't go join other ppl SOS, especially those very hard to join elder investigation, buat kacau only

Either he got carried or troll. Some people like to die just to fail troll the mission. Nerg probably one of the easiest elder, vaal is easiest.

currently farming the Triple Threat Takedown event for decorations. so nice

still no heroes streamstone for me, after 150 hours in the game

You know whats infuriating. You try to join a Tempered SOS session but you get an error and all of your SOS settings reset. What the actual **** Capcom lol.

try again few more months down the road, doubt we will get those instant SOS anymore even during tempered investigation

New event can craft kulu helmet

how long this game will receive support from capcom in update and new monster ?

if more than a year,thinking to buy ps4 pro along with the game since currently only play at ps4 game cafe

from my pov,monster hunter asset in term of monster and elder dragon can last more than a year.Releasing one elder dragon from older game each month can last very long period of time

Yeay! I've just unlocked the 'Augment Equipment' at the Smithy. Just in time before going out. Hehe! HR64 at the moment.

Addendum: Anyone augmented Zorah Magdaros full set armour? Is it good? Seriously thinking of getting mine augmented.  Nergigante full set is fugly.

Vaal hazak set is great. Only have one teeny tiny little bit of weakness, fire. As almost all enemy in the game use fire.

Trivia, with 14 fire resist and 200 hp, you can survive 3 bagel bomb back to back. With negative 14, only 1 1/2.