Good day, summoners! I'm on the North American server, and am always looking for more people to play with! I can't claim to be particularly amazing (I topped out at a bit above 1400 this season and have wobbled downwards in the days since), but I like the game and like playing with friends. Message me if you're interested and we can discuss game times. However, I am currently taking a break from the game as my internet has been maddeningly inconsistent, and I'm tired of inadvertently screwing over my teammates.
As for the discussion at hand, I'd like to throw in my own opinion about the relative power levels of various ultimates. In general, I think Riot does an excellent job of tying together the skill sets of each champion. Because an ultimate is, by design, much more powerful than a normal skill, it isn't surprising that they're often referenced as a significant part of what makes a champion what it is. Take Poppy, for example. Her ultimate places her in a category all her own simply because she becomes functionally invulnerable for 6-8 seconds simply by using her ultimate against the least threatening member of the enemy team. Between that and her passive reduction of burst damage, she can become very "tanky" while building pure damage.
I would, however, say that certain champions are significantly more reliant on their ultimates than others. Darius is one of those who is quite reliant. The base damage is abysmal, in theory, but due to the bleed amplifying it up to a full double the normal damage, it can often take a good quarter-to-third of the health of an equivalent level, non-health stacking champion. Without it, on the other hand, Darius has to pick between damage and durability, and isn't particularly amazing at either. He suffers the scaling issues faced by all AD casters while possessing worse ratios than most.
Discussed earlier was his penchant for being banned. I think that this is largely a problem at lower skill levels, as his gameplay is relatively straightforward while offering high rewards. He isn't that difficult to play against, due to his absolutely hideous immobility, but doing so is, in my opinion, harder than playing as him.