The last couple of issues of the Grayson run were written under heavy, heavy editorial intervention.
The Tarantula resolution wasn't in "the last couple of issues of the Grayson run" (which, yes, had heavy editorial intervention. They wanted her to tie in to Infinite Crisis, which meant major changes to her plans). As for Tarantula herself, Devin said that Tarantula was both a hero and a villain, that she was always meant to be a negative influence on Dick's life, and that she was always meant to go to jail (Devin had originally planned to have Nightwing convince Tarantula that her actions had been wrong, showing [not telling] her why you can't use violence to solve violence, and get her to go to jail willingly. But when it came time to wrap things up [and I'm very much paraphrasing Devin now, since it's been a good while since I read what she had to say] she decided that was too simple and happy an ending for Dick, and he shouldn't be able to redeem Tarantula). If you want to say Tarantula was a bad (or at very least poor) idea, and that she was executed VERY badly? I'm right there with you. But self-insert? No.