Tinker is a very flexible hero that just "helps". Decent attack, a solid active, and an AoE damage signature - which is hard to come by in Black. He may not fit into decks with a razor sharp purpose, but Tinker can at least do 'something' for any strategy.
Tinker's attack of 7 is the "expected good amount" in Black, only bested by the buffed values of Debbi's 9 and Phantom Assassin's 10. His health, to say the least... is literally LEAST.
Laser is on the upper tier of hero abilities. 3 damage and a disarm is very relevant, and just having it up forces your opponent to respect it.
Disarm essentially removes a unit (hopefully hero) from combat. It's what makes this active so potent. Don't just use this to pick off unimportant units - the disarm is EASILY worth saving 6+ health.
Trying to maximize this by using it each time it's up is not always correct. The fact your opponent has to play around it is a huge thing. It's easy to think you 'maximized' it by using it twice 'that game', but could a single more impactful usage have been better?
A mini Conflagration, that also does 6 damage to tower? Not so bad right?! While it's easy to brush this off as a worse Conflag, there are many games the tower damage component is relevant.
Looking deeper, this isn't even much worse than Conflagration. If placed ASAP, it will expire in either turn 4 (mana 7). Even if you killed zero creeps or your opponent abandons that lane, you still did 6 to their tower.
Keep in mind this does nothing if you cast it in the current active lane, since it triggers before the action phase.
Tinker fits into any deck, but is he the best possible fit for the slot? He does a lot of things, but may not be worth it for decks with a very specific purpose.
You wouldn't (can't?) build around Tinker - there's simply no identity or synergies to build around. If you're in colors without a solid AoE option, I guess that's one of Tinker's only unique properties.