With the recent addition of phase 2 to Mists now is the time to level alts!
Reduced experience requirement
The rate at which you gain experience from level 85 to 90 has been increased. They’ve changed the bonus amount from 10% to 65%. This is effectively a 50% increase in experienced gain, which means the leveling time is reduced by about one third compared to know. This means you can now level characters a lot more effectively. The tiller farm alone is quite valuable for some easy alt goldmaking, and as we approach the Throne of Thunder the value of alts will go up!
Daily cooldowns galore
Both the two last phases of Mists Classic will add a significant amount of new daily cooldown recipes. These are used to craft various new epic recipes and are for the most part bind on pickup. The daily cooldowns will also unlock new PvP recipes. All of these leads to a situation where having more high level alts is a lot more valuable.
Blacksmithing in Throne
The main new cooldown in Throne of Thunder is the Blacksmithing Lightning Steel Ingot. That means you need to level the prospective alts to level 90 so you are ready to rumble. The new recipes require some Spirits of Harmony, where you need 30 daily cooldown materials to get a max level 502 weapon and it will require 18 spirits of harmony. If you have a max level Tillers farm going you will easily be able to sustain and even have some spirits left over for other recipes.
Daily cooldowns
For leatherworkers you get a new daily cooldown for crafting Magnificent hides. These are used in a ton of new PvP recipes and will likely have much higher relative demand next phase. The daily cooldown can be done with either leather or scales, so stocking up on whatever the cheapest one is right now can be quite valuable, particularly if you are a leatherworker. The main recipe can only be done with Leather so I expect the scale option to be quite cheap as leather demand will go up with the increased hide demand.
New epic recipes
The new epic recipes for phase 3 are also gated behind these daily cooldowns. In addition to various high end materials (Imperial Silk, Living Steel or Magnificent hides) they cost Haunting Spirits which you get from disenchanting Throne of Thunder gear. It is a guaranteed drop so the price will likely be very high early on, but trend downwards allowing these crafts to be consistent profit makers.