This weekend I tried to level up a void elf mage post 8.0. Most of the mods were broken during this experience. My setup is full heirlooms minus the pirate ring from the fishing tourney, 60% xp boost.
Since it was an allied race, you start at 20, and get dumped into the real world quickly. This has its upside and downside. The only real downside is you do not get full xp from the starting zones. I like to go back and do the starting zones because the rep gain from them helps on vendors across the world. Were I to start from 1, I would do all the starting zones for full xp.
I tried out war mode. What I was expecting was on level fights by people in the zone. What I got was 110s on flying mounts dismounting from flight and one-shotting me. Mostly they would kill you 1-2x and move on. But in Duskwood there was a full party of 110 idiots with a wallock porting buddies in and killing all the quest givers. Overall it seems like an OK trade off as long as they do not camp the quest hub. If they camp the hub, go to stormwind, toggle off, and come back and wrap up. The other problem seems to be the cheap shot, where you are tabbed out looking at a quest description, or you are in dialog from turn in and they chump you. Mostly rogues and stealthed druids seem to do ths. Because I was sitting at +60% xp, the extra 10% from war mode is likely not worth it, and I did not notice much increased rewards. But if you are bored with the usual quest grind, and you are doing off the beaten path questing, it is worth it. Works better with Mage since you can port to SW, and bind to the quest hub. Still can pull it off with the guild cape that gives you a SW port on 8hr CD.
I enchanted my heirlooms. I logged over to my enchanter, looked down the list of stuff I could do by piece, and applied to scroll the enchants and mailed them. There was no level usage on the 110 enchants, and was having the mark of the satyr? proc off of the necklace functioning at low level. Definitely worth doing for all the heirlooms you use.
I started as fire, then switched to arcane mage. Even with all of that stuff on, I was taking about 4 casts to down stuff, or 3 if I was using arcane with a full stack of arcane blast. I know how to play fire and double cast with instas in the last 5% of a cast bar to fish for hot streaks, but simply arcane is stronger and you can turret and cast faster. You have less CC and worse AOE, but mostly for questing you are doing single target.
Dungeons are not worth it now for 4 reasons: (1) the queue is really long as the player base seems to agree they are not worth it now, (2) war mode toggles off and that is the new thing, so there is no benefit to the toggle, (3) tank threat is lower so tanks are having to work harder to hold agro, and (4) looks like they put crowd control back in the mix, and there is a huge learning curve there that most have forgotten. I got more xp faster by chaining quests, and the dungeon grind has been the thing for so long it is worth dumping it. The only reason why I ran anything was to cap Stormwind rep with a tabard to reduce the cost of flying training.
I made my void elf mage on Fri, and by Sunday I was 66. Classic WoW zones felt slower, mainly because weapon power is less than it used to be. Lich King from 60-66 also felt slow. I got 6 levels just fully completing Borean Tundra. So there is that. I did not try out Burning Crusade to see if it was faster there. Before 8.0 Northrend was better than Outland.
Because of the caps for zones were elevated, I think a good strategy is to get a guildie to port you to Dalaran, bind there at the portal hub, then do the starting zones. Those zones are meant for unmounted questing, and mostly the PK types stay out of them, and I think you can maybe get a huge chunk of rep and xp doing them.
Then do the 1 off zones with War Mode off if you are in a high PVP zone like Goldshire. Again all of these zones give plenty of xp, and the layout and completion is fast, with still more rep. Then cycle through the 2 off (2 zones progressed from starting area, where you still get rep gains). I bet if you do all of that, you will be pretty far along towards 60, and you will have resolved a lot of the classic rep grind without having to do the dungeon queues.
I would keep war mode off from 40ish to 60 or so, and stay in classic til 60. Outland/Northrend is much easier with a flying mount, and you can likely go war mode on with a flying mount. I did Borean with War Mode off, so the next zone I will try it on. Again Howling Fjord/Borean Tundra are good picks because the layout was designed for ground mounts and you can fly and rapidly complete otherwise difficult quests. I think most of the predatory ganking is heavy in 1-off zones like Goldshire, and the usual rep train people follow for Stormwind makes Westfall/Goldshire/Redridge/Duskwood a gank heavy zone. There was a lot less traffic in the Night Elf areas, or the Draenai areas.
I took enchanting. There are changes to it. You can now disenchant any level item regardless of your enchanting skill. This means that you can take it as a quasi gathering profession now, grinding up quest rewards for mats. I would otherwise take gathering professions, as raw mats are going for crazy prices now for old world areas. For instance a bolt of silk was going for 6g or so. You can either gather and sell for coin, or support other characters with your gathering on the way up.
Void elf with the no spell pushback from interrupt is a powerful thing, and works well with Arcane where they can not stop your arcane blast. However, it looks like they stripped out fire/frost from arcane, so if you get arcane locked, you are screwed, and so you likely need to do the usual run away stuff that you needed to do prior to 8.0. The rift teleport thing they have is basically a juke move for pvp. There is little pve value to it. That plus blink + displacement are an arsenal of juke moves to screw up melee from staying on target. Basically send VE rift the opposite direction you are running. If they follow you, rift that way and create space. Works well with the arcane ability slow too.
So on the list is war mode in Northrend. I might try an Outland zone and compare xp gain there v. Northrend.