Huh? How are you getting a +16?
+5 from your stat (+5 total)
+3 from prof (+8 total)
+2 from combat adv (+10 total)
+2 from leader (+12 total)
Even tossing in Action Surge, thats only +3 for +15 total.
Well, Fighters get an extra +1 because of Weapon Talent. My Dragonborn Fighter has a Strength of 18 and uses a Battleaxe, so lets look at his stats.
+4 from stat (+4 total)
+2 from prof (+6 total)
+1 from weapon talent (+7 total)
+2 from combat adv (+9 total)
+2 from leader (+11 total)
Now, if you give my Fighter a sword (+1 additional prof bonus) and a 20 strength (+1 additional ability mod) then he'll have a +13. That's at first level with normal weapons of course.
Now, normally my Dragonborn Fighter would have a +7 to hit enemies with no mods. Going with the 17AC that Thomson used, he would hit on a 10 or higher. This gives you the 50% hit percentage that the system was supposed to approximate. Basically, they want the players to miss once in a while, but they still want you to hit a lot too.
Now, anytime you go beyond this +7 via either a higher ability mod, higher proficiency bonus or additional modifiers such as combat advantage, you will hit
more than 50% of the time.
So, when you're trying to use something like one of your dailies, you're supposed to try and engineer situations where you're less likely to miss. Such as gaining combat advantage on the enemy and then having the Cleric hit him with something that will grant you a +2 to hit. This will take me from a +7 to a +11, which would mean I would only need a 6 to hit AC of 17. If the big bad guy had a higher AC though, like a 19, I would still only need an 8...which is very doable.
Assuming I'm using Villain's Menace (which is my level 1 daily that I selected), I would then add another +2 to my +11, bringing the total up to +13 against that enemy for the rest of the encounter! So now I'm hitting on a 4 or 6, as long as I can maintain combat advantage and the Cleric keeps hitting with her spell. Even if the Cleric is missing and the big baddy maneuvers out of combat advantage, I would still have a +9 to hit against him, which would mean I'd hit on an 8 or a 10.
And this is just level 1 and concentrating on only 2 abilities that would give bonuses. There's no magical weapons involved, and no feat bonuses. It's very doable to increase the odds of a hit even more. And say my Fighter only had a 16 strength? I could change to swords for the extra +1 proficiency point and still be at a base of +7 to hit and be hitting 50% of the time.