Guild Wars 2

The ranger is clearly supposed to receive a substantial portion of its damage from pets.
However, pets have proven unreliable and inconsistent in providing said damage given any number of factors including:
1) AI
2) Ability to Avoid and pathing (like AI)
3) Speed at which they die
4) Animation speed etc.

So what happens and would it go to far if rangers were allowed to have BOTH pets out at the same time (so swapping provides a second set of 2 pets)? In what situations would it be quite fair and in which would it be unfair?

Roaming is an obvious situation where having 2 pets attack you would be difficult. In dungeons, WvW or even small groups, pets would still die fairly easily. OR at least, the consistency of the damage of pets would be lacking. And, frankly rangers and roaming seem to go hand in hand to me.

Scale of 1-10 how good/bad is this idea as it should be easier to implement?

I don’t think adding a pet will solve the problem.

Let’s take #1 and #3 of your assumptions, and let’s assume that pets deal ~40% of our DPS. One of our pets dies during a dungeon, we’re down 20% DPS. Both of them die, we’re down 40% DPS, the same situation we are in at the moment with just one pet. You can switch, but the point is “pets would still die fairly easily,” and there would still be plenty of times where we would be down from our full DPS.

There’s also problems like pet damage balancing, trait balancing, and the fact that you have another pet to worry about and micro-manage. I don’t see it as a particularly easy thing to implement.

If you’re thinking, “Oh, maybe staying at 80% DPS sometimes might not be too bad, it’s a lot better than 60%,” they could just make the pet still attack while it’s down, but deal 1/2 of it’s original damage, with decreased abilites — an “easy” fix, IMO.

But that falls into the realm of actually improving pet features, not just adding more mediocrity. Quality over quantity.