I disagree with that statement. Champions mobs, See Invisibility, or True Seeing have absolutely no effect on your stealth play. I play stealth characters all the time, and with the exception of stupid spiders, I can sneak almost from 1 to cap. However, there is three major problems with stealth right now, that you forgot (I agree with the "not group-friendly"):
1) Invisibility is a major necessity while sneaking, if you don't have Hide in Plain sight. While I understand the monsters getting bonus to spot while you stay stealthed in plain view, invisibility makes them DO NOT get this bonus. This is incredibly useful while you are watching a patrolling mob to learn its path, or when you NEED to cross somewhere when the guards just never turn their faces away.
2) Other than Assassinate (a level 12 ability), there is no advantage from alpha striking from stealth. Sure, you get sneak attack damage, but in DDO this is not enough to one-shot a mob. Heck, it is not even enough to make a mob take reasonable damage to start with 30-50% HP left. Bosses even less. I'm not saying that everyone that can sneak behind a mob should be able to one-shot it, but rogues should had a huge boost if hitting something INACTIVE. Leave sneak attack to DISTRACTED mobs, and give a huge boost (huge for rogues, big for monks/rangers, good for the rest) if hitting anything that is not fighting someone else, searching for a noise, or charging into battle.
3) Stealth is plain broken at low levels because the mobs get bonus to spot too fast. When your hide skill is very low, and you don't have many ways to improve it yet (like wielding a Cutthroat Smallblade), staying on a mob's sight for 5 seconds is enough for them to detect you. And those low level mobs, made back when the level cap was 10, move A LOT around the dungeon, because at the time, stealth mechanics were based more on ambient light than your hide skill.
I know many people don't care about the starting levels, but when your new player want to try out stealth mechanics and is spotted by every kobold guard they meet, they will assume stealth is plain broken, and join the bullrushers.