Like you said it's combo reliant but it's only a combo. The heroes themselves are fine but they have very little pick off potential(minus glimpse)
1: Terrorblade is absolute stupid with dragon lance, and it's not like he was bad before this just made him absurd. I find him to be one of the best carries and hardest to counter as an offlaner because he's so damn tanky with 12(?) starting armor. If he gets a pms like I do then you do almost no auto attack damage to him.
2: Puck is great at fighting in the mid game while your terrorblade is farming up the items he needs. Rotating with a support(or both) and you can get pick offs pretty much anywhere and create the space you need to have your TB come online faster.
3: You can go a couple different ways with your offlaner/third core. One way is single target lockdown, in which case a Beastmaster would fit that role greatly since primal roar is one of the best stuns in the game(also bkb/MI piercing). Team fighting oriented you could go either void(my personal favorite) or a dark seer since vacuum works well with dream coil(either setting it up or triggering it).
4: Depending on how you went with your 3 pick, it's the opposite(more or less). Having beastmaster available for roar either forces a fight to happen or it's a pick off and you're able to push off it. Either way, having an enigma jump in and really turn the fight your way with a good blackhole is great or having edilons push/tank a lane is a great way to force down towers. If you have the void/darkseer, Phoenix is still really great this patch. Sunray and chrono is almost a guaranteed kill, and supernova pairs really well with dreamcoil AND vacuum. Besides that, Phoenix is great at rotating around and helping out lanes with crazy heals or gap closing for a kill. If not
5: You have push, you have initiation, and you have disable. Your team is fine, so as a cherry on top I like Oracle. Great babysitter, and pretty much as soon as you Oracle hits six, the terrorblade(shouldn't) be dying. Sunder works through False Promise since it's coded as HP removal, so as a gimmick the terrorblade can essentially bring someone down to 25% health(the minimum) if the Oracle gets the false promise off well enough. Even without that, phoenix sun ray does 16 + 2.5% heal. Doubling through false promise is 32 + 5% per second(at max level). If TB dies through that then it's over - either you lost since you're getting stomped(unlikely) or they lost since the rest of your team is running through theirs trying to bring down a raid boss.
That's just my dream squad though. He's not picked very often but I'd like to see Oracle in pro games more since his ult alone is just so strong. You get anyone with a heal and it makes it impossible to deal with, and god forbid he gets picked with a huskar. That's some cancer I would never like to face up against.