That may be true, but I'd also be interested in hearing the best argument for the alternative.
You haven't presented yourself a single argument as to why would the Dominican Republic want to do that at first place, how would that benefit them exactly?
Only Haiti stands to benefit from any "unification". And more importantly, the Dominicans should be the only ones to determine their destiny; not academics who think "improving economic status" is a valid reason for merging one country with another -- without any regard for the preservation of culture, ethnic makeup of the country, history, national identity -- and most importantly: values.