Although I kind of suspect bad blood with Guggenheim (not with Amell, as she and him seem to get along well), I also thing godisawesome is on the nose with his evaluation. Also note how they returned somewhat to her "bland Audience Surrogate" portrayal in S4. She was less snarky and more of a moral compass for all of Team Arrow. And Sara seemed more like your typical CW female in S2 than Laurel did, too.
I kind of take Sara and Laurel's arcs in Season 2 as evidence that Arrow's writing team does its best work with shorter, succinct arcs based around resolving certain character threads, rather than long arcs that stretch for seasons. Sara's initial arc was basically Oliver's Season One arc in an abridged form, almost literally beat for beat; it mostly acted to focus the action so the audience got to know the character while the writers and actress fine tuned the character. And when Sara returned as a near main cast member, they
did start writing her as a more common CW female protagonist.
But that first arc gave her a strong foundation, and the overall effect made her feel like a fully fleshed out altruist we could cheer for, since at her core she was Oliver's opposite number and equal. She was closer to him in archetype than just about any other character in the show. So while her interactions felt more like common CW fluff, she was still a highly active figure in her storyline.
Laurel, on the other hand, had what mostly amounted to one perpetual subplot throughout Season 2; she's stuck in a character arc moving at the speed of molasses about Tommy's death and her issues while Oliver adopts a no-killing rule, streamlines Team Arrow, becomes a traditional superhero with a mask, reveals a history of fighting extranormal opponents, rediscovers Slade alive and well, and loses his mom. Her subplot lacked focus and pacing, and that's why it stunk.
Incidentally, I think that same problem plagued Seasons 3 and 4, though in different ways. 3 simply drug everything out far too long, from Sara's murder investigation to Merlyn's reveal, to Oliver's subplot on recovery from the climb, to the final conflict with Ra's. It no coincidence that arguably Laurel's best arc was the best arc of Season 3, when Brick is the main villain for a short but tightly paced arc and her arrival as a full fledged vigilante arrives with some genuine power. And Season 4 had a great villain, but almost wasted him with how long he opposed the heroes.
If the writers take too much time, they tend to tread water, and that plagued Laurel far too much in Seasons 1-4.
