dear bill, the AHD (as at bartleby.com), for one, is very consistent with the 'strophe' words, putting the accent on the second syllable:
a NAS tro phe
an TIS tro phe
a POS tro phe
ca TAS tro phe

hence
e PIS tro phe
or NITH o tro phe :)
pe RIS tro phe

but
SYS tro phe
and
STRO phe
8)

p.s. - where there is an adj. form the major accent almost invariably changes to the penultimate syllable; e.g., cata STROPH ic