How big is your map? If it's still too slow after you've amortized it over a frame or two then I'd guess it's an implementation issue or you're running it too

How big is your map? If it's still too slow after you've amortized it over a frame or two then I'd guess it's an implementation issue or you're running it too often per entity. At least assuming your graph size is <1000x1000 or so, then the above should generally hold true... That said, flow fields are fantastic tools too.