Other issues that come into play are the nature of the engine failure - is the fan and/or the core windmilling, or have they seized? (Are they even still there - if the fan rotor disk failed there may not be much left of the front of the nacelle at all.) All those possibilities can drastically affect the drag produced by the engine(s) and make a nonsense of any engine-out performance you may have.
Also, if you start losing multiple hydraulic systems, you may have to contend with things like spoiler panels upfloating if they are no longer being positively held down - and thus potentially yet more drag.