This looks like a bug to me.

I can get the optional rule elements to work when followed by COMMA, as follows.

DECLARE Feedback;
(W{REGEXP("change|modify|alter")} W? W? W? COMMA) {-> MARK(Feedback)};

This would match the following.
change the current rubric,
change the rubric,
change rubric,

But if I have a W or a W with REGEXP as 
the element following the optional elements, it 
doesn't work.

DECLARE Feedback;
(W{REGEXP("change|modify|alter")} 
W? W? W? W{REGEXP("rubric")}) {-> MARK(Feedback)};

Doesn't match the following. (it should)
change the current rubric
change the rubric

But it would match "change the the the rubric" 
(when words occur for optional elements)

I've seen that there has been a similar issue sometime back: 
https://issues.apache.org/jira/browse/UIMA-3338
Not sure whether this issue related to that bug.

I'm using UIMA RUTA workbench 2.3.1 on Eclipse Luna (4.4.2)