Try going to the develop menu...floating info windows...Show Selection tags. Then, find and check all the solo mode abilities, and press OK.
On the list of tags for each one, make sure that everything looks right.
If not, try adding debugs to your script:
Code:
<!-- Hide us if we don't meet the required rank -->
<eval index="1" phase="Initialize" priority="10000"><![CDATA[
debug "Checking: " & field[name].text
debug "Our rank is " & herofield[acRank].value
debug "and we require rank " & field[ReqRank].value
if (herofield[acRank].value < field[ReqRank].value) then
perform assign[Hide.SoloMode]
debug "This ability was hidden"
endif
]]></eval>
Look at the debug output (develop...floating info windows...show debug output) and make sure all the field values look correct.
The first thing I'd suspect is that your script is happening so early, that herofield[acRank].value hasn't been set yet, so it's value is 0.