The issue leaves me somewhat torn. There's no way around the fact that Karthis is right; mods like these -- and they exist for several classes -- make it possible for players to do great, or at least acceptable, DPS without understanding the class and spec they play. They also have the side effect of encouraging tunnel vision on the mob/s rather than what's happening in the raid (and, as someone who plays a tank, I must admit I hate dealing with an utterly oblivious DPS). Nobody wants to see a lazy player rewarded with excellent DPS for no other reason than their ability to install a mod and then do what the mod tells them to do.
But another part of me wonders if the difficulty of these rotations (e.g. the feral Druid, the affliction Warlock, etc.) is being determined more by the limitations of the UI than anything else. For example, I play on a laptop with limited screen real estate, and keeping track of my debuff icons on a boss when they're even smaller on a laptop than they are on a proper monitor is hell. For a while now I've been using a mod called BadKitty that, while not a "suggester" mod of the type Karthis is describing, makes it significantly easier for me to see exactly which debuffs I have up, and how many seconds I have left on them. While something like BadKitty probably isn't objectionable because it doesn't tell the player what to do, here's the rub; I gained about 500 DPS using it. Suddenly I knew to a tenth of a second how much time I had to store energy for an upcoming attack, and I could put that information in a useful place rather than squinting at boss debuffs.
So frankly I do wonder about the extent to which certain DPS rotations depend on assistance from mods in order to be viable, and where the line is between "OK" and "Not OK."
** For all those of you who don't play a feral Druid, here's where Karthis is coming from; the cat DPS "cycle" is a set of priorities for buffs and debuffs (Mangle, Rake, Rip, Savage Roar, Tiger's Fury, Berserk, with the abilities Shred, Ferocious Bite and Feral Faerie Fire when feasible/necessary) with severe penalties for allowing debuffs to fall off. Because energy is a constant -- but not very fast -- tick, you have to be a fairly skilled Cat to go the length of a boss fight without missing a debuff timer or allowing energy to go unused. It's very difficult to time abilities like Shred or Ferocious Bite to consume energy without affecting the next debuff you have to refresh, and it's not uncommon for Druids to to let energy pool for fear of missing a crucial timer.
The Druid mods that Karthis mentions are actually fairly clever programs that utilize some complicated math to determine which skill you should be using and when, and notifies the player to activate the ability. So, the appropriateness of their existence aside, they represent an inspired bit of programming (and the people who wrote them know the Druid class backwards and forwards), but they do throw a wrench in the idea that the greatest contributing factor to your damage will be skill.