The last is especially important for your dyslexic readers. I have heard of dyslexics who can not puzzle out the name and so go by the first letter. Some can puzzle out the first few letters, and others the first letter and the general shape -- but variety helps them.
May be impossible in a long work to have fewer than 26 named characters. (Worse if your setting has no fitting names beginning with X or Z or what have you.) But varying them can help even there.
The hero or the heroine, or even major characters, I chose the name with care, partly because knowing the right name -- with all its attendant baggage and expectations -- helps define the character. But bit characters -- well, before I use them all, I look down the character sheet and chose the first letter of the alphabet that hasn't started a name yet, if I have no ideas for a name. It helps limit the search.
Once I get over a couple dozen, I find I have to go through and count how many start with each letter. Then I go for the unrepresented letters. If I don't watch out, the names will cluster on one -- or at best, two or three -- letters.