Sarah Darkmagic’s point is well made about the Essentials martial classes (except they aren’t called “builds” anymore, snap). The new powers seem to be deconstructions of the original powers for the 4E Rogue. The previous class construction provided a consistent form for each class: 2 at-wills, X encounter powers, Y daily powers. The same for every class (until the later books dropped). Now, with Essentials, we see variation among the classes in their access to different power types right off the bat. Thieves, for example, don’t get daily powers.
Instead, Thieves have a variety of at-will Tricks up their sleeves, and rely on their basic attacks augmented with their Backstab encounter power for their attacks. If I understand Sarah correctly, she is arguing that this leaves something to be desired on the tactical field of battle. Let’s compare, shall we?
A 5th-level 4E Rogue has a total of seven class powers (2 at-wills, 2 encounters, 2 dailies, and 1 utility), plus the Sneak Attack ability, which augments six of those seven powers with additional damage based on the presence of combat advantage against the Rogue’s target. A 5th-level Essentials Thief has six class powers at a variety of levels, but no daily powers at all. Only encounters and at-wills. The Thief does get two uses of its Backstab encounter power at 5th level, so that gives it approximately seven class powers at 5th level. On the face of it, in quantitative terms, the Thief and Rogue seem even in raw options.
The Thief, on the other hand, has three Tricks. These are all move action powers that give a variety of situational benefits to the Thief. The Thief’s arsenal at the beginning of combat also includes a utility power; the encounter power, Cunning Escape; and two uses of the Backstab encounter power. Only the Backstab power incorporates an attack, so the Thief is free to use its full action as it sees fit: most often a basic attack. The Thief has Sneak Attack too, although it only augments two powers: its two basic attacks. In total, the Thief has six options, discounting the Backstab’s double use. Clearly, the Thief build is no less simple than the Rogue and arguable more complex when taking into account the other features the class gains over the first five levels (including Weapon Finesse, which allows the Thief to optionally use Dexterity or Strength for melee basic attacks; and Skill Mastery, which can be very handy in combined combat-skill challenge encounters).
As the tactical combat plays out, the Thief shines in terms of variety even more. The Rogue has just two at-wills and two encounter powers—4 total options from which to execute at the beginning of combat. Those options decrease as the battle rages on and the Rogue extinguishes its encounter power uses. When the Rogue extinguishes its uses of encounter powers, it is left with just two at-wills and most likely one of them is just an attack with added damage. The Thief, on the other hand, has its same complement of attacks (basics), but three total at-will Tricks. Each class has a utility power that could be either an at-will or an encounter power.
The Rogue does have an advantage over the Thief against monsters with low Reflex defense. A lot of the Rogue’s powers target Reflex; the Thief’s basic attacks always target AC. This seems like a prime place for a series of Feats that change basic attacks to optionally target different defenses.
Now you may be asking about daily powers at this point. Of course you are! How can I discount everyone’s favorite powers? Well, in my experience there are two ways daily powers get deployed: 1) wait till the boss fight to blow all your dailies, or 2) use no more than one an encounter (at 5th level). Daily powers can turn the tide of a given combat and make for very dramatic gameplay situations. I think the core of Sarah’s argument, which she obscures with a lot of tangential evidence, is that the Thief doesn’t have daily powers and those big moments are really important for a lot of players, possibly even her. Certainly a lot of 4E players. I agree. However (there’s always a however), the Thief’s Backstab ability I would argue accounts for some of the loss of big-bang oomph by giving a sizable attack and damage bonus that stacks with the Sneak Attack ability— +3 to-hit/+3d6 damage is nothing to sneeze at, especially when you can do it twice in every encounter!
Is Sarah’s claim a strong one? I don’t know for sure because I haven’t yet played a Thief (and she has). So my argument has to be taken with a grain of salt. But given the construction of the classes, it seems that there is ample complexity in the Thief class waiting to be unleashed on the tactical battlefield. If combats drag out, the situational Tricks of the Thief become more likely to occur and it has more of them, so it tends toward more variety on the face of it. What the Thief gains in tactical usefulness, it loses in big-bang oomph. No daily powers make it seem on average less effective as a striker.
Can we execute cool moments with the Thief like we could with the Rogue? Well, that’s up to the DM and players. The rules have little to say about cool imaginative stuff like kicking bad guys off cliffs other than the golden rule: have fun playing D&D!