It's Cancel with a Flamecast Wheel-like spell attached, so I guess we have to look at both parts before looking at it as a whole.
Is this a good card? I guess, but it's no Counterspell. Well, it's a counterspell, but it's not the Counterspell. It's a solid back-up, but not really a good choice for a main counterspell, mainly due to the cost. You want to be able to counter stuff as early as possible, and turn 3 may be too late against some decks.
Is this a good card? No. No it is not. There is no reason to run this card. If you have space for it, run a Forest instead. Even if you don't have any green cards, a Forest will always serve you better. However, its badness has to do mostly with the fact that it costs a full 6 to use. If it was 1 to go down 2 to activate, then it would be a lot better (sort of like an improved Moonglove Extract).
So, back to Suffocating Blast. It's made of an okay card and a bad card, albeit if both of those cards were cheaper, they'd be better. So, if we divide the cost of Suffocating Blast amongst its two components, it basically becomes a Counterspell with a slightly weaker Searing Spear. So, the question becomes: is a Counterspell with a mini-Searing Spear attached in one card good? Yes, it is. My only major issue is that it's very colour-intensive, so it's basically relegated to the world of Izzet decks. The cost is high, but since it's 2 cards in one, that is to be expected.
Cons: Costs 3
Pros: Colourless damage
Cons: Costs 6 for 3 damage to a creature
Pros: Counterspell with creature damage
Cons: Colour intensive, costs 4