I ran my group through it tonight. They were rolling terribly, so that was definitely a major factor. They made it to that encounter, and got slaughtered. They probably should have pulled back after clearing the outside. They were able to finish off the first group well enough, but when the reinforcements showed up, they were too depleted and got whittled away after a couple of rounds.
There were only four players in the group, and no one chose the cleric, which, in hindsight, put them at a serious disadvantage. They should have run, but I don't think they thought there was a chance of them dying. I'm a pull-my-punches kind of DM, but I wasn't doing that tonight; I wanted to see how tough combat could be, so I could see how much I should feel willing to fudge it when we get our real 4E campaign going.
Also, while I was running the kobolds to their fullest, my players took a bit to get a hang of all their options. Even then, they didn't have enough time to formulate a decent strategy before they were hit hard by that encounter. Taking a different route and engaging some of the other lesser encounters would have given them more time to mesh as a group and discover their strengths and weaknesses.
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Honestly, it seems like you're better off mucking about in the first couple areas of the keep and leveling off of those before you tackle A3. A2 lets you wade through a swarm of janks, and after A1, you feel like an effing hard-ass. Momentum will lead you to want to dive right into A3, but even though it comes in waves, A3 is still a really tough fight for first levels. If I was to recommend the best course of action in the early stages of the module, it would be to check out the dragon grave, then explore the first few areas of the keep, then go after the kobold base. Also, don't be afraid to withdraw after clearing off A2. Now, if you follow any one of these recommendations, you are a bad person. This is more like off hand advice to DMs on how juicy they should make their hooks if they want their party to survive past the first few encounters. 4E characters have a lot more potential for awesome than 3E ones, but it takes some time for that to sink in with players used to 3E, at least in my experience.[/sblock]