Nostalrius Begins - Quality wow vanilla realm (1.12)

I'm currently leveling a shaman as elemental. If auto attack is enabled while I cast (with no break), I'm still able to get a melee hit between casts.

1) Is this how it is supposed to work, or is it a bug?
2) If it is a bug, is it a violation of the rules?
3) If it is perfectly fine to do it, is it worth it for e.g. raiding as elemental?

For number 3), I realize that Elemental is not the best choice for raiding, but I don't care for now. The reason I ask about this, is that, as least while leveling, the auto attacks with a staff provide a significant amount of the damage I deal: At level 26 my LB hits for 140-160, and my staff + Flametongue hits for about 70-90 damage. I realize the damage done by auto attacks compared to LB/CL is a lot lower at max level than at 26, but I still think it might provide some extra DPS from doing practically nothing.

The topic has been touched a bit in this thread, but no conclusion was ever found.

It's intended, it also worked like that on vanilla retail. Casting offensive casts doesn't reset the swing timer. Casting a defensive cast such as a heal does reset the swing timer.

It's 'worth it' during raiding depending on the situation. Some bosses have mechanics that forces melee to run in and out, then it's not worth it. During trash clearing you don't want to run 30/36 yards before you start casting, it's quite a huge time loss. Sometimes bosses have a melee range AoE ability, then it's also not worth it because it causes pushback to your spells.

During tank n spank fights where you can get into position before the boss engages the tank it's certainly worth it, there aren't many of those.