I tend to avoid writing dialogue with an accent. I do find that it looks a bit plain, and sometimes writing, "Allo' there, pleased tah meet'cha!" Seems more colourful, I'd just rather write plain and describe how the character speaks.
The GOT series has a lot of colourful accents, but I sometimes found myself re-reading things just to fully understand what someone was saying. Not that it was bad, because I do love those books.
The worst thing about this book is the one character who speaks 17th century English. There is a plot reason, but it's definitely a bit overplayed.