Ok Sadrik, instead of bickering about the feel of this change, lets see what the "math" says.
Lets create two characters: Bob the Fighter and Joe the Wizard.
Bob has an 18 str, fights longsword & shield, and the rest of his stats are negligible. He picks Cleave, Tide of Iron, Reaping Strike (human), Spinning Sweep (all E) and Brute Strike (D)
Joe has an 18 Int, 8 str, 12 dex. He has a crossbow and a a wand implement. He picks Magic Missile, Ray of Frost, Cloud of Daggers (human), Force Orb (all E), Sleep and Acid Arrow.
Lets do some comparisons.
At 1st level, the fighter has a few interesting combat options. If two foes are lined up, he can hit one for 2d8+4 damage and his buddy for 4, he can push a foe and move (along with his 2d8+4) or knock the foe prone and do 2d8+4. Or he can once/day do 3d8+4.
His average damage with one of his attack is (4.5 x2 +4 or 13 damage). If he fights a level 1 foe, like a kobold skirmisher (27 hp/13 bld) He could effectively take him down in 2 rounds barring a miss (one attack bloodies, one attack kills). In one encounter, he effectively opens with four 13 point attacks (+/-) before resorting to his 8 pt basics.
Joe, Otoh, begins with magic missile (4d4+4, avg 14), moves onto ray of frost (2d6+4, 11 hp), cloud of daggers (2d6+4, 11), and finally force orb (2d8+4, 13 + 1d10+4, 9, adjacent) Again, assuming all four hit, he's done average damage of 49 damage to the primary target (as well as slowed him for one rd and done 1-2 pts of dmg from CoD). His first two attacks nearly cleaned up our kobold skirmisher.
In fact, If Bob and Joe were out-numbered 2-1 by skirmishers and did the "always hit/average damage) they could take out the kobolds alone in five rounds tops without resorting to their dailies. (total damage output from their eight encounter powers: 101 hp, total kobold hp 108) and this is ignoring the residual damage from CoD and the carry-over damage from cleave, as well as OAs and APs.
And that's two PCs alone; add a rogue (with his sneak attack dice), a cleric, and another striker (lets say a warlock with eldrich blast and warlocks curse) and those poor kobolds are toast! Probably in three rounds without resorting to a daily.
I guess that solves the "combat-speed" problem too.
Now, here are more things to consider:
1.) Are all encounter powers equal? At 13th level, you must swap out an encounter power to gain a 13th level power. Do I get to swap out one of my "super at-wills" because in a choice between retaining 4 damage to adjacent foes, push a foe 1 square, and knock a foe prone, I'm fairly certain I'm keeping "knock a foe prone" because its more universally useful.
2.) Humans get a bonus at-will as a racial feature (as Joe and Bob show us). So a human starts with four encounter powers. Sweet. We're keeping that right?
3.) Because if you do, you have to fix some of the other races. Half-elves get an at-will from another class as an encounter power. Do they still? Is it sill an encounter power? If so, they're nearly as awesome as humans (depending on stat of other-class power). Or is it a daily now?
4.) More importantly, dragonborn's dragonbreath is only 1d6+con starting, and is clearly inferior to nearly any of our super-at wills (making humans a much better choice, or half-elves if we keep dilettante an encounter power). My suggestion, of course, is to boost dragonbreath to 2d6+con starting, and raise it +1d6 over the character's life as normal. There are some other races like this as well (firesoul genasi and probably more in the MM) that would need dice bumping.
5.) Does our ban on "at-will" magic apply to class features (like paladin's divine challenge or a wizard's cantrips?) as well? If so, kiss the paladin class goodbye.
6.) Similarly, certain utility powers (like the Rogue 2 powers Fleeting Ghost or Great Leap) is at-will. Encounter?
7.) Oh yeah, mult-classing feats?
The big thing this system does is encourage you to open with all 3(4?) of your encounter powers for the most damage, the clean up with basic attacks. The effect is moot. Every time you begin a fight, you want to launch your 2 dice attacks first, then resort to your 1 dice basics. This has the effect of watching your party go nova for 3+ rounds, then resorting to chipping away at weakened, bloody foes. Then rest 5 minutes and do it again.
This, of course, will get worse when your PCs hit paragon and have eight or more encounter powers to burn through, then resort to chipping. It will get better in epic though; those 2 dice super-at-wills will be useless damage (equal now to their basics, which go up to 2 dice at 21st) and probably only recalled when their secondary effects are useful (like slow or extra damage to adjacent foe).
If you DON'T double at will dice, your making the fight even LONGER. The wizard is expected to be doing 1d6+int damage min every round (barring misses and excluding magic missile). If he does it three times and resorts to his inferior crossbow, the fight lasts longer because his to-hit is lower (more chance of missing) and his damage is lower (much lower in some cases).
Neither promote tactical use of encounter powers: go nova and get it over-with.
If you think you can live with the repercussions, go for it man. I just think as soon as this see's field-testing with live PCs, all bets go off and you'll see a lot of "three rounds of encounters, now lets slowly chip away with basics" fights.
Just breaking your system before your PCs do.
