The Heat probably aren't going to move Bam (or Butler), have very little in draft capital, and can't trade Dragic for awhile, so they basically have to include all of their young players i.e. Herro, Robinson, Nunn and then need Olynyk and Iguodala for salary. If that is the best you can get from Miami, then you don't make that trade. It does improve if you put Dragic in there instead of KO and AI, so maybe mid-season that trade is revisited, but I still think I'd rather have some combination of LeVert, Dinwiddie, Allen, Kurucs, Prince, Shamet, Brown than that trio from the Heat. Again though that isn't a good trade for Houston. Heck given that Houston has none of their own 1st's, I think a package centered around Middleton actually is a better deal for the Rockets as there is a pretty good chance that no one you acquire from either Miami or Brooklyn ever becomes anywhere near as good as Middleton. Middleton, DiVincenzo, Wilson, Patton for Harden. Since Houston can't rebuild, that trade is probably better than Miami or Brooklyn.
At the end of the day though, I think Houston just hopes that the Sixers start of the season looking bad and eventually agree to Simmons plus some draft picks. Or that Boston decides that it wants to go all in around Tatum and puts Brown + Smart + some 1st's on the table. Those are clearly better trades than anything they could get from Miami, Brooklyn, or Milwaukee, and since they have 2 seasons, they can afford to wait a bit and see what shakes out. Also, I know they haven't shown an inclination to trade Harden to a western team, but I could absolutely envision a team like Denver getting desperate and wowing the Rockets with an offer. I mean a package that includes both Murray and Porter (add Monte Morris and PJ Dozier and the money works) would have to be seriously considered by the Rockets and if I'm the Nuggets it is something I'd have to consider as well as a Harden/Jokic duo would be incredible.