No, not at all. I'd definitely put Hvar on the list. Split and Dubrovnik are each pretty different, but they're not that big so a full day in each place (two nights on each end) and you can really have them covered. If you stayed longer, you'd mostly fill in with relaxing on the beach or taking a ferry to some islands or drinking ... Islands are always more relaxed and more conducive to hanging out and meeting people so save time for that. ZAG is so-so, but not worth giving up time on the coast or in the islands for ...