Where did you read that I am arguing about DK being inferior to NB?
I was just pointing out that comparing, what you exactly proven, that stealth is free and available to everyone, to the only quasi counter, which is magelight, is simply not fair. Magelight takes a skill slot, has cost in terms of resource and static % sustain on magicka + requires putting skill points into it.
If stealth was also an active skill, that you need to place on the bar, like for example NB's invis, then I would be fine with this being the only real solution to the stealth in the game. As it is, it's not a 'fair' playground, as right now the only viable tactis is basically travel in very large groups with some guy wasting a slot on magelight, or traveling yourself using stealth when in a small group or alone, OR sending 1-2 players as a bait and have pack of stealthed guys being next to them...
Anything else is not smart.
I'd change a passive detection range to 10-15m so you still can attack from regular maxed range of bows, staffs and most of ranged skills (ca 20m) and perform scouting missions, while Magelight buffs that radius for another 15meters and detects invisibility within 10m radius. Add also a rule that if you break stealth on PvP by dealing damage, you cannot re-stealth for 1min versus other players.
Problem solved, stealth is balanced, and magelight is actually a good skill investment.
PS. Just on the note, I've also abused this ability myself during the beta destroying tents and siege equipments of other alliances while being DK in HA, but I know that it was an abuse and I can call it.