Crafting is the creation of items without the direct involvement of combat. That definition also tells you the principal problem of crafting in an MMORPG: It competes with getting items from looting. If you could craft the same epic item that some raid boss drops, there would be a diminished interest in raiding. But if you can't craft anything half decent, then why bother with crafting at all? Thus MMORPGs over the years have used a lot of half-baked crafting systems and always had problems getting the balance between items from crafting and items from adventuring right. One typical bad solution is to make crafting indirectly depending on combat: The epic you can craft needs a recipe or component that only drops from the raid boss. Unfortunately that of course removes all the interest in crafting from the people who were interested in it *because* they saw it as a chance to get good items without having to raid.
To allow a crafting system to produce items which are useful, the design of that crafting system has to contain some sort of obstacle to overcome; otherwise players can just mass-produce more of those items than anybody needs, and the value of crafted items tends towards zero. Many games use a system of crafting skill points and the difficulty of gathering resources as obstacles. That does not work very well, because at the same time gathered resources and crafted items are the basis for the player-run economy. Thus if armed with a sufficiently large stack of gold, a character can level up a crafting skill from zero to level cap epics in an afternoon, just running between auction house, mailbox, and crafting station. By making the obstacle based on a tradable currency, players can make crafting trivial by obtaining that currency via higher level characters or even from gold farmers.
So what obstacle, what non-tradable currency could be used to make it impossible to take shortcuts on crafting? Time! Time is the ultimate currency in all MMORPGs and other online games, because each of us only has 24 hours a day. While "time spent playing" can vary by an order of magnitude between players, that is still better than gold, which can vary by several orders of magnitude. And once you make the obstacle mostly real time instead of time spent playing, everybody is equal.
And this is how companion crafting in SWTOR works: To gather a resource or craft an item, you have to send your companion away for some time. I only experienced low level crafting in the beta weekend, where that time was some minutes. But that could easily be expanded to hours or even days for crafting an epic. As an added obstacle, you don't have your companion available to help you fighting as long as he is out crafting or gathering (although I don't know how that is handled once you get several companions. Can you craft with one and fight with the help of another?). Crafting also needs credits in SWTOR, but I would guess that the time requirement will be the main obstacle. While there will be undoubtedly "SWTOR crafting guides" to be found on the internet plotting the fastest path to maximum skill, somewhere in that guide it will say how many hours and days that takes minimum. And as there is no queuing of crafting commands, players will even take much longer than this minimum theoretical duration, because if their companion returns while they are offline, they can't send him again before logging in again. If you wanted half a dozen "crafting alts", you'd be busy all day just logging between characters.
I do think this is a very good system. Yes, it will annoy some people who want instant gratification. But it will allow others to actually craft items of value. And it will make crafting an important part of your main character, instead of being a task outsourced to an alt. I believe that crafting in SWTOR will be a lot more meaningful than in many other games. And that is quite an achievement.