I've been working on some very similar builds, basically the first 2 talents might be swapped depending on the situation.

With no talents, you provide a 5% bonus to the damage of your team with the Hunter's mark (4s uptime * 25% + 16s downtime * 0%)/20s total duration.

Level 1:
- Ranger's mark is giving you and your team 8.3% overall damage (4s uptime * 25% + 8s downtime * 0%)/20s total duration
- Seasoned marksman is giving you, if you can stack, an average of 10 to 15% damage and 0 for your team which is about 7 to 8% extra damage if you include your team in the math

So for level 1 Ranger's mark sounds slightly better unless you are sure to stack up over 15% of attack damage with Seasoned marksman which is about 30+ stacks at level 20
Therefore on maps where you cannot stack up (remember it has been nerfed with the patch and objective minions don't count anymore) it will be weaker.

Level 4:
- Focused attack will grant you 6% increased damage in the worst case scenario (if you do not attack and reduce the cooldown) which is about 1.2% extra damage for your team
- Searing arrows adds about 8% to your personal damage output if you land all your attacks on the target and that'd be about 1.6% extra damage for your team

In my opinion, Searing attacks gives you a better power in the early game because you are attacking slower and so your Focused attack is not refreshing as fast, but this talent is incredibly mana consuming, needless to say that if you'll be useless if you have an Abathur on top of your head as you'll be oom most of the time.
On the other hand, the Focused attack is mana efficient and when you hit that 60% attack speed increase you'll be able to land 2 to 3 focused attacks in one burst. If for some reason you get Abathur, with the auto attack buff, on your head this is definitely a better option as you'll refresh the cooldown super fast and be mana efficient.

In the end, it's a matter of what you feel more comfortable with, I'd preferably go for the Ranger's mark at level 1 because :
- it syncs your stun and your shredder (12s cooldown each)
- it gives you more utility especially if you have delayed damage dealer in your team because you can put the mark on the target (ie. Kael's living bomb, Jaina's blizzard)


I've been crunching some numbers for the last couple of days, I hope I didn't get to deep in this ^^, keep in mind that the numbers above are statistics and basically calculated on the scenario where all your team is focusing the same target and you are constantly shooting and using abilities...

Cheers

It wasnt a bad build but the problem is it builds and builds for the late game so much that early and mid game you are just really weak and so is your support from heals. Once you get 20 though I think you can surprise some people on how fast you do dmg.

Focused attack has been buffed some months ago and it gives 75% damage bonus, Fire arrows is a ****py talent now..

Mnesymne is correct i just tried it and bye bye mana.

That's probably because at an attackspeed of 2.00 atk/s it would drain your mana in an instant then you can't use your control/finisher

You didn't take fire arrows at level 4 ? It's better for "burst" a squichy one no ?