You sound very emotional. The way you feel about invokers seems to have convinced you that you are right, and thus you are unable to see your reasoning is ultimately flawed.
1) Hellstreaming unsanced necro here.
He is standing there in NEXUS LAG. He can't move. He can't do anything. He can however get autoassist attacks from all of his zombies, along with his own high damroll weapon. So this is the perfect situation to use this technique. Its a complete gift horse, and Kavion blew it by just spamming his damage spell instead of using it skillfully. Spamming 1 spell is not what AR's invokers were intended to do - why the hell would you spam hellstream vs a player like that?? They're not mobs where they just instant-attack you for fleeing. The game is changed a lot by the simple fact that a PC is subjected to LAG (like NEXUS LAG) that prevents him from doing that. And the scope of that is a lot wider than just hellstreams. You can do it to warriors when they miss dirts, or bash your shield unsuccessfully. Or whatever.
2) the technique is not useable.
Other people who have played invokers at level 50 have used it without a lagged opponent. All you need to do is flee constantly and keep opening the fight, and 50% of the time you will get what you wanted (1 round of damage back before you flee). With a little practice you can get significantly beyond 50%, and one thing that makes that EASIER is drow/elf. Heard about all those awesome elf/drow invokers? Graykun, Jerold, Zemnahn, Thkot, etc? This is what makes them awesome - their sneak allows them to get first attack in. iT sure as hell isnt their 16 con with crap parry. This is not something you have to resort to because your class sucks.
* What makes this possible is that hellstreams lag is 1.5 rounds, instead of always 2 rounds, or always 1 round, its sometimes one or sometimes the other due to the way those lag times last over rounds depending upon WHEN you casted them.
You should be able to figure out WHY this works better than mindless spam, otherwise you will always suck with your class, like Kavion here did. Clearly from your response, you haven't done so yet.
So.. You could listen to the masters of the game telling you WHY they don't suck. Or you could cry like a baby because a skiller warrior player pulls off a flee/murder off inbetween your lagging hellstreams (3 rounds of strong melee vs 2 round crap mage melee + a saved spell - seriously, the potential for uneveness is awesome here), easily outdamaged your ass because you were all +hp no +dam/+affbreak, and then rant on a forum someplace that your class sucks in defiance of evidence otherwise.
Conclusion: Don't be so emotional and do the math.