Wobbly splined cranks, yet bolts are very tight I have a road bike with ISIS splined cranks.  I've been noticing front derailleur rub lately, and when I took a look, both of my crank arms are wobbly.  The retaining nut is very tight, so tight on the drive side that I can't even back it out.

The bike is an entry level bike equipped with Shimano Sora. Except for the crankset, which is an alloy crank from (Taiwan).

I checked the BB by seeing whether the wobble transmits to the other side, or to the crank axle.  It does not.  Each crank independently wobbles.  From what I've read, this implies that the crank splines are worn.

I am thinking the most conservative move is to replace the cranks and see what happens.  The most aggressive repair is to replace the entire crankset, including BB and chain rings.

Are there any options that I have missed?
Sounds like wear between cranks and bottom bracket.  Strange its the same on both sides, I'd expect your primary foot side to be more worn.

Have a good look at the interface between crank and BB.  Look for wear and witness marks to see if they're worn together or just the BB or just the cranks are worn.

You shouldn't have to change your chainrings unless they're a one-piece unit with the right-hand crank.