Great minds think alike, that's exactly how I did it. ^^
Though I used the Critical Pain devestator to do massive damage to her body when all her tentacles were down.
I died once, and that was because I thought that running in and slicing like usual would do the job, but I reconsidered, looked around, saw tall buildings and went for the Aerial Graveyard Spike plan.
Farily easy fight really, none of the bosses, like you say, have any real attack patterns, it's all just random, to the point where it's insulting.