+2 from lvl
+5 from dex
+4 from +1 kukri
+1 from Expertise
+1 from Thief Weapon talent
+2 from CA normally
+1 from Nimble blade.
Essentials is off the charts for to hit for a few classes including the Thief. Your assessment is correct.
In your list here:
+5 from Dex is a +1 boost over most other PCs because a 1st level Thief can get away with a 19 or 20 whereas many other classes need multiple decent stats.
+1 from Expertise, the purpose of Expertise is to balance out a math problem. In reality, the fix should start at level 5, not level 1 (the earliest this can be taken). So, it's good to know that at least this +1 will be less of an issue at level 5 and above than it was at level 4 and below.
+1 from Thief Weapon Talent. This is a culprit here. Fighters used to be the only class with Weapon Talent, but now Thieves get it as well.
+2 from CA. Getting CA slightly over half of the time when the game was first designed was an average of a little over +1. Getting it every single round is an additional +1.
+1 from Nimble Blade. This was often a staple of Rogues. But, it only occurs when Combat Advantage occurs. When the game first came out, this +1 was conditional. CA didn't always occur. With the Thief, it almost always occurs. This makes this feat more potent because it really isn't conditional for a Thief.
So, the Thief now is easily capable of being an average of +3.5 to hit over the original Rogue and even more over other Strikers. That is a problem for some players and DMs. Hitting often is fine. Hitting 95% of the time against a same level monster? Why exactly are we rolling the dice? Oh yeah, to see if a 1 or a 20 shows up 10% of the time.
There are entire combats where rolling the to hit die for a Thief is meaningless.
And of course, with the change to Sneak Attack being every turn instead of every round, people might as well play a party of Thieves and never be challenged.
So, if the original Rogue did d6+5+2d6+1 damage with CA 2/3rds of the time with an 80% chance to hit and d6+5+1 damage 1/3rd of the time with a 65% chance to hit for an average DPR of 10.9 (without crits), the Thief now does d6+5+2d6+1 95% of the time or 15.7 DPR (without crits) and he can sometimes do this twice or more per round (and of course, not including other feats to boost the damage more). That's an increase of over 40% more damage and even more with the Sneak Attack change. And people claim that Essentials is balanced.
As the PCs go even higher levels, he'll gain 4 (or 5) for stats, 5 for magic, 2 for expertise, and 13 for level or 24 or 25 over the next 26 levels. More or less, he'll always be up in that 80% to 90% range to hit forever (without even taking into account bonuses to hit from allies or other abilities).
Another issue here is that DMs used to challenge PCs with n+2 through n+4 encounters. With the damage change for monsters, this pushes a challenging encounter back down into the n through n+2 range which means that all of the PCs are effectively +2 to hit, further exacerbating the to hit issue.
It's pretty much a shame that WotC blew off their promise from Aug 2008 to not have a boatload of stackable bonuses to hit in the game system.
PS. A +1 Kukri is only +3 to hit. Be glad that your player took that weapon. Not that it matters that much. He misses a same level foe on a 2, but hits on a 3.
