Szarala is 100% correct in terms of mechanics; the fight represents a great many aspects of warlock that have almost no place in day-to-day operations.
It's like creating a tricks track for racecar drivers and saying that the guy who can land his jumps and drive on two wheels is the pinnacle of race-car driving; in reality, the two are very different skillsets that happen to use the same equipment.
There are a great many aspects to this fight that the vast, vast, VAST majority of warlocks (and players in general) probably don't even consider before entering the fight (or reading up on it, in most cases). The very simplest and most pervasive example is the threat drop from the gate debuff; without the existence of this fight, at a guess 99% of warlocks would happily go about their business not knowing that it works that way, because it simply doesn't matter in almost any real-world application.
The fight requires quite a high level of technical capability in terms of any given pve encounter in the game (applying the right solution to the right problem with the right timing), and it is thematically perfect for the warlock. Assuming you don't grossly overgear the fight you have to be a reasonably good player to get green fire, but calling it the "pinnacle of being a warlock" is a farce. The pinnacle of warlocks are on the cutting edge of raiding progression and in the highest of arena ratings and rated BG play, where abilities that are part of the practical toolset of the warlock, and not gimmick ability bloat or secondary effects to what is a primary purpose, are put to use.
The "ultimate warlock encounter" is any given difficult PvE fight that tests the pinnacle of players, or any PvP fight at the highest of ratings, probably against whatever is seen as a counter-comp. You can't put the warlock in a vaccuum, arbitrarily assign worth to abilities that had none prior, and take that to increase the "worth" of the fight. Trust me, if I can do this fight at 470ish ilvl like I did, it does not represent the pinnacle of warlocks, because I suck at warlock. I am, however, great at reading instructions, following timers, writing macros, and putting appropriate buttons on appropriate hotkeys.