I use XP elimination (“lock your XP”) for every expansion. Usually, I do the first map to collect some needed base gear, then unlock XP and then level up to the next level threshold that unlocks the next expansion. If you do everything in an expansion you get 4-5 times the XP you need to unlock the next expansion. It’s plenty.
So for instance, for Outland I do the first map locked at level 60, then unlock and level up to level 70 on the next 3 maps and after that lock XP again to stay on level 70 and finish the other maps. I do the same for the other expansions.
A lot of quests in the old expansions are bugged. And I mean a lot. Old mechanics that once worked are broken now. Like an old sword that magically once removed 80% of an enemy now only remove 10%. And you end up with something still 10 times your HP. It’s bugged, it’s not solo’able at low level, after a while I stopped being frustrated about this. Many other quests spawn too many mobs or the HP of small mobs is too high. It has nothing to do with combat skills, once a quest spawned with 20 enemies each 10% of base health, now the reduction is missing and you have 20 enemies at full health. Or quests require you to use AoE but over the years AoE damage was so much reduced that it’s no longer possible in time. That’s a few examples of quests that once worked but now require help.
I keep a list of quests I need to do, including group quests and once in a while I get what I call a “level 120 obliteration toon” from a friend to help out. I usually try to still do the quests myself and when my HP is very low (because it’s not possible for me anyway) he one-shots the boss. That works. Or it’s a healer.
For phased quests all I can do is mark them and return when I’m 12-13 levels above. Nothing else works, not even party sync, the new feature is completely useless. Party sync is really the most useless feature recently added to the game. When it’s on, half your quests are disabled, you cannot pick up all new quests, and phased quests (when you really need help) are all not working with it. It’s a different story, it’s completely useless. It is a great idea, but just an idea; it has been implemented in the most useless way possible.
And for other players to help: I my experience at the start of an expansion you have a lot of those speed levelers, that can’t get bothered with anything. They are rude, sabotage your game play and are really the most negative thing about WoW. I wish there was some phase thing or whatever where Blizzard puts those so they can annoy another. There is no point in asking anyone for help, they just insult you. But, if you move on to the next maps, they are all gone. You are left with those players that play for story, not for speed leveling. There you can easily ask for help, there’s always someone that has a few minutes to help out. I myself always have a few minutes to help out.
So far I managed to complete all expansion quests but at times it’s frustrating.