While both of these players have been great at one point, they seem like a square peg round hole scenario.
Howard even now is a better big man on D than anyone we have on this roster, but he's now 30 and banged up with issues of knees, and he had that back issue a while back. Yes, KG was thought the same way, but Howard is no KG when it comes to the approach of the game. While it's nice to have a paint defending Big man, this team needs a go to scorer out side of IT and some times ET. I'd much rather have Hayward than Howard for one part scoring and two parts better personality/youth.
Harford is a good all around player and 3 years ago would have been jumping up and down if there was a chance, but with him being 30, he's not long term, and not a guy who could bring an other name to the team.
DA has things these teams may want and thats, cheaper/younger players who can be resigned for less than either Howard or Harford will go for, expiring contracts and Picks.
DA may be looking at players that are partly young, but longer term. Like a Cousins(don't think hes even close to on the table), Griffin, Love. Why wouldn't they just trade with each other and leave Boston out of it. Well they could, but Boston has one thing both team can use and thats draft picks for cheap players since both team are maxing out. And Boston could have some decent picks to give up for the right deal.
Plus Cleveland owes DA for helping out with getting Lebron and Doc owes us for the mess up that prevented us from getting Jordan, even though it may turn out to be a better deal with Brooklyn.
Now I don't think 100% this is the idea, it could also be DA blowing smoke up other GM's butts to get an other deal going. But I just don't see Howard or Horford helping us beyond this or maybe next year. Unless they come on the very cheap, just too pricey.