Looking back at my last few games I could have definitely used this strat to do some funny things, like getting units up in the enemy's face turn one or, like I said, using it to surround them with Flesh Hounds. Or even get around their army completely and get something in their back-leader's face, which would have made my life easier on a number of occasions (Flesh Hounds assaulting some wizard that thought they were safe behind battleline units, hue hue hue).
If I'm not being clear for other users: since you're summoning the units one at a time you can use the new leaders (cheap, small foot heralds specifically) to increase your summoning range. Because you place your summoned units down one at a time, you can "chain" your summoning across the board with one or two heralds before dropping something larger, like Flesh Hounds (this assumes eight total blood points for two heralds and one unit of five Flesh Hounds). This could also allow you to squeeze out of sticky situations where your opponent thinks they've got your leaders stuck in such a way that you can't summon, depending on the amount of blood points you have available to you. All you'd need is enough room to drop a herald (which are on 32mm bases, so pretty small in AoS terms) which should give you enough room to then summon what you actually want (Flesh Hounds or Bloodletters).