there is some merit in ws'n in over TP as it adds to y/g/k and fudo FTP mod's and it'd be hard to make a comparitive quantification for hassashin vs meditate, in the realm of mission fights and boss type battles though i find lower meditate recast to be more valuable, that is to say from a utility stand point.
as far as hassanshin goes i personally stand to gain over 48 extra per strike with full ikishoten merits, 43 @ 4/5, but a 1.??% increase to that would likely be negligible, much like double attack and crit rate zanshin rate + is going to have diminished returns.