I've been levelling up a new character by doing quests in shadowlands and started taking notes which quests now give huge xp/sk rewards (same as daily missions). The list is incomplete but I'll try to update it later as I complete more quests... I haven't tested these quests with 200+ level toon so don't know what kind of SK rewards you'll get.
Note that in lower SL zones some quests have max level limit on them - all should be doable with char below level 150 except in Nascense where level limit is 50 for some quests.
Shadowlands
Nascense
Garden Quests - 2x daily reward each key
Elysium
Garden Quests - 2x daily reward each key
Guards
Guard - Elmo Fitz
- 1st quest 1x mini-xp reward 950k xp (kill 3 devourers)
- 2nd quest deliver item 1x mini-xp reward (950k xp at level 137)
Guard - Ulf Reinhart
- predator scanning 1x daily reward
- deliver item 1x mini-xp reward (1M xp at level 138)
Yuttos
The One Loved by the Sun - 1x daily reward and 1x mini-xp reward
One Who Overcomes Enemies
- Kill named Malah - 1x daily reward
- Kill each Elysium catacomb boss - 7x daily reward
One Who Gives Light - none
One Who Has Achieved Glory
- delivery 1x mini-xp reward (1M xp at level 138)
- Extermination trip to the Swamps 1x daily reward
- A hunt for the Somphos horn 1x daily reward
One Who Has Taken Vow Of Truth
- Deliver an Ancient Text 1x mini-xp reward (1M xp at 140)
- Find Excalibur's End 1x daily reward
- Find the frozen artifacts 1x daily reward
- Searching for your roots 1x daily reward
- Soul Feeding 1x daily reward when completed following missions:
- Kill 10 Cagey Hoathlans no reward
- Kill 10 Fissure Hiathlins 2x mini-xp reward (1.1M each reward at level 143)
- Kill 5 Malah-Behns no reward
- Kill 3 Hoathlans no reward
- Kill 3 Brisk Hoathlans no reward
- Kill 2 Malah-Anas no reward
- Kill 1 Malah no reward
- Kill 1 Malah-Dren 2x mini-xp reward (1.1M each reward at level 143)
- Kill the Hiathlin Lookout -> return item for quest reward
Shades of Grey
- Help Shades of Grey 1x daily reward
One Who Wins Over Mind
- Bluetooth fungi harvest 25k xp
- Fight the Looting Mortiigs 1x mini-xp reward (1st quest part), boss quest part ??
- Get urgently needed mixture ??
- Up for a challenge 1x mini-xp reward (1.1M xp at 144)
One With a Graceful Neck
- Searching for truth 1x mini-xp reward
Scheol
Ocra Garden Key Quest - 2x daily reward
Jobe Scientists - each quest step 1x daily reward (total 10x daily reward)
Adonis
Xan Civilization quests
One Who Points the Way
- Talk to One Who Greets Wanderers - 1x mini-xp reward (1.3M xp at 149)
One Who Greets Wanderers
- Kill 3 Stingers + Return with fish treats - 300k xp + 1x mini-xp reward (1.3M xp at 149)
- Talk to Fourth Watch Down - none
Fourth Watch Down
- Find a 4 different spirits - 1x mini-xp reward (1.3M xp at level 151) + 300k xp
- Talk to Conserver Gil Gala-Hume - none
Conserver Gil Gala-Hume (clan)
- Kill 5 Boran-Kaar - no reward
- Kill 5 Cimi-El - no reward
- Kill Biran-Keir the Custodian - 300k XP (if solo)
- Return to Conserver Gil Gala-Hume - 500000 XP + 1x daily reward
- Talk to Mr. Free - no reward
Scott Free
- Give shards to Scott Free - 150k xp + 1x Mini-XP reward
- Destroy Amok Baraton - no reward
- Return to Scott Free - 300k xp + 1x Mini-XP reward
- Talk to Dr. Aleksander Koumas - no reward
Dr. Aleksander Koumas
- Clear the dig site entrance - no reward
- Kill Ruins Defender - no reward
- Kill Ruins Protector - no reward
- Return to Dr. Koumas - 700k xp + 1x Mini-XP reward
- Talk to Dr. Marko Steffensen - no reward
Dr. Marko Steffensen
- Kill 5 Sizzling Synaptid - no reward
- Locate a Lone Shark - no reward
- Give 3 specimens to Dr. Steffensen - 600k + 1x daily xp reward
- Investigate mysterious creature - no reward
- Return tissue sample to Dr. Steffensen - 850k xp + 1x Mini- XP reward
- Talk to One Who Gives Warnings - no reward
One Who Gives Warnings
- Get mixture from Jackson Turnfloat - no reward
- Mix up some Soothing Mixture - no reward
- Return Soothing Mixture to One Who Gives Warnings - 400k xp + 1x Mini-XP reward
- Scan Heckler of Elements - no reward
- Scan Heckler of Harmony - no reward
- Scan Heckler of Dreams - no reward
- Scan Dormant Golem - no reward
- Return to One Who Gives Warnings - 1x Mini-XP reward + Yutto's XP-reward
- Talk to One Who Remembers The Past - no reward
One Who Remembers The Past
- Kill 4 Numb Eremites - no reward
- Kill 4 Brisk Dryads - no reward
- Kill 4 Malah-Dors - no reward
- Return to One Who Remembers The Past - 750k xp + 1x daily reward
- Talk to Mourning Calamity Five - no reward
Mourning Calamity Five
- Kill Tower Keeper Tagnat - no reward
- Return to Mourning Calamity Five - 1.5M xp + 1x daily reward
Garden key quests
Ecclesiast Gil Jha - clan garden key
- The Lost Diviners - 1x daily reward
Diviner Gil Yeol-Ulma - clan sanct key
- The Lost Diviners - 1x daily reward
Dark Ruins - solo
Jobe Investigator George
- Gain the Trust of the Cultists - 7M xp
- Tell Jobe Investigator George about what happened to Hilda and Gunda - 7M xp
- Give the Cult's Holy book to Jobe Investigator George - 7M xp
- Kill the Spirit Goddess - ??
Bob
- Kill 10 Climbing Creepers - 7M xp
Administrator Tanja
- harvest the energy from 5 Notum Saturated Rafters - 7M xp
Administrator Ivar
- collect plant samples - 7M xp
Spirit Guide Hinnerichsen
- Escort Cultist Loke to Spirit Guide Hinnerichsen - 7M xp
Special Agent Hansen
- Storm the ruins - 7M xp
Hilda's Spirit or Gunda's Spirit
- Talk to Hilda's Spirit or Gunda's Spirit - 7M xp
Penumbra
Garden key quests
Cama Garden Key Quest (clan) - 2x daily reward at the final step
- Phase 1 - Get to know the land: Steps 1 to 10 - 30000 XP, 5000 credits each step
- Phase 2 - Gather Evidence: Steps 1 to 4 - 40000 XP, 5000 credits each step
- Phase 2 - Gather Evidence: Step 5 - 2x daily reward (about 16.5M XP at level 169) + 500k XP + 500k credits
Xan quest line
- 7 or 8 daily-rewards (total amount uncorfirmed, info by Fatalfox)
...more to come...
Most of these quests are easy to complete on 110-150 characters and completing the above quests + other daily missions + doja chips you can solo level up your character quite fast (10 or so levels per evening).