Something done once is never griefing.
Doing it over and over, yeah, I expect that would get dealt with.
When players engage in same-faction griefing, it would be nice if GMs had an option to flag them red to their faction for a day or so. Then there’d be a PVP solution!
Summoning Infernals is no more annoying than POM Pyro blasting people out of the blue. Or really any other pvp activity. This could happen anywhere in the game world. Contested zones were places where the two factions seem to collide. Crossroads and Goldshire also had some action as well, but I don’t recall it being excessive.
When I was playing Shaman, I talked some players in STV into waterwalking over to where Deadmines was. We ended up having an epic pvp brawl outside the instance, but I never did get into Deadmines until I rolled an alt in Cataclysm.
It takes more than a spell with an hour cooldown to grief a zone. However, it should be easy for an admin. to spot such bad behavior and deal with it as appropriate.
I did this all the time back on Nost, it would usually last like 5 minutes before some high level came and killed it. Most of the lowbies found it hilarious or interesting at the very least, though I did get a few illiterate angry whispers. I also got lowbies to help me summon doomguards, most of them saw it as like a world event that broke up the monotonous grind I guess. The only messages I got from GM’s is to not summon Infernals on roofs (I once had 5 on the Goldshire roof) and to not summon them in the starting areas like Northshire.
I think summoning them in a remote questing hub or near quest mobs would be bad though because they would probably be there for hours. My intentions weren’t to harass people or to inhibit leveling, just liked to stir things up.