Written as a long group, the claim will be invalidated by finding something in the prior art with anything on the list (and otherwise satisfying the claims). Written individually, only the single claim with that item will be invalidated and the rest will still be enforceable.
You can use a numbered (actually lettered) outline form and repetition of wording for clarity. Claim 1. A method for doing something the method comprising:
(a) making square widget comprising:
(i) petting the widget to make it square;
(ii) kicking the widget to make it submissive;
(b) hardening the made square widget.
Another approach is
Re 1. Please note that clarity is quite subjective, therefore some examiners would object to the clarity of a claimed whereas some others would not. You may find some guidelines about clarity here and there, or manuals handed to examiners, but beyond subject-matter that is objectively unclear, pretty much you cannot say for sure whether the examiner assigned ...