As I encountered the TV series first, and read the books second, I never had any issue with Bean not being the tall, blue-eyed, long black-haired & facially scarred cockney of the novels, but if readers had already built-up an image of the character in their head which jarred with Bean’s look, I can understand that.
However, I don’t deem the casting of Bean or his accent to be failures. He encapsulated the gritty toughness, leadership & intelligence of the character believably, and that to me is much more important than slavishly casting an actor primarily on looks at the possible detriment to performance.
Bean’s own accent did the job well in firmly demarcating him from the cut-glass speech of the officers with whom he often clashed. I’d rather that than actors adopting a cockney accent for the sake of it. Many otherwise good actors make complete hashes of accents and badly distract from the character. Of course, some can do accents with aplomb. And then you have Sean Connery, who’s in a category all of his own...
I thought that Sean Bean was an interesting choice for Odysseus in the film Troy, and that he did a very credible job.
About accents. I use a text to speech program quite a lot. The computer generated speech is made from bits of a real person's speech. I have a number of "voices" for it, but the one I use almost all the time is a Scotch voice. Not Glaswegian, I believe, but still a pretty strong accent. I use this voice for a couple of reasons. One is that since I have to accommodate the accent anyway, I find it easier to accommodate slight mispronunciations or other mistakes in parsing the text. (On the whole, the program is pretty good, however.) The other is that the voice is part of a series that is supposed to be more natural, with more inflections and the like. So, even when listening to hard boiled detective stories set in California, the voice is Scotch. It doesn't bother me at all.
Best wishes,
Bob