It can be punishing if you chose a healing spec first, having to wait till 102 to get other Artifacts.
Leveling in a heal spec in general is not the path of least resistance, but by the time a player reaches level 100, hopefully they would know this, and take it into account when they make the decision. It's no more punishing than leveling in a heal spec would be in any other circumstance.
Also, you don't need an artifact to level. You still have the option of using regular weapons (previous expansion level 100s or the class-specific greens from the vendor in your class hall), which should be perfectly adequate for leveling. The levels come pretty quickly, and you will be back on track with another relic soon.
It can also be punishing if you're that Utility player that plays all specs of your characters. Raid needs a Tank? change from dps to tank. Sure you can keep the relics updated, but it's difficult to achieve a 20 in all artifact points, early on. I would have rather that the points be a blanket level. So that if you change your spec you have the points allocated differently.
The choice of which weapon to pursue first is supposed to be a choice that matters. These are legendary weapons that are essentially being handed to us for far less effort than we used to have to put in for our first blue at level cap; we're supposed to think about it a little before choosing. A player is not supposed to be able to play a DPS spec exclusively from day one, then one day decide to become a tank and instantly be just as well-equipped as someone who was in a tank spec from the start.
Still, it's not hard to make up lost ground. When you first get your relic weapon at 100, it only takes a few hundred artifact power points to go up a rank, but the points come relatively slowly too. As the weapon increases in level, the artifact power needed to gain a rank increases geometrically, but the rate that artifact power is gained increases too, especially after the player reaches 110 and begins artifact research. It isn't very long before world quests are awarding a thousand or more artifact points... which is barely enough to move the progress bar toward the next rank on the first weapon, but enough for a couple of ranks on a newly-acquired relic. You can catch up pretty quickly that way.
It used to be that to change specs, you usually needed a new full gear set. Tanking gear, DPS gear, and healing gear were all separate. Now the armor is universal within a type; all mail gear items work for ranged agility-based DPS (hunters), melee DPS (enhancement), caster DPS (elemental), and healing (resto). The burden of having to assemble a full new 14-piece armor set for the new spec has been waived... all we have to do now is level the free legendary weapon we got a bit.
I sure hope my quotations and formatting make it through... since there is no preview available and no option to edit posts, TS...