MIAMI — “We have enough to get the job done.” Erik Spoelstra has said it before, will say it again, but at the moment it also might be a reach. No sooner did his team suffer its second 20-point loss to the Celtics in the first three games of this best-of-seven opening-round Eastern Conference playoff series that now has Boston up 2-1, then the Miami Heat’s glass-half-full coach opted for optimism. The reality is not only were the Heat without and will remain without Jimmy Butler and Terry Rozier, but lately have seen diminished returns from Duncan Robinson and Kevin Love.