As a Hillary supporter, should I take this as a concern that the Clinton campaign is getting complacent, especially with the risk that the news cycles could turn against her, if she get more cocky, and loses the swing states (most news has her winning 300+ elec. votes?
Personally, I wouldn't think this would be a cause for concern. I do think that it's a good thing in fact as she would be able to win more states?
For the record, Arizona has constantly been a swing state, but Texas is leaning-Republican.
Below are the reasons --
Firstly, she does have the required states to win "locked up". She can afford to lose some a few swing states and still win the presidency. According to my calculations, she is poised to win 269 electoral votes which are Democratic-leaning states where she has been constantly leading in polls, while Trump will win 164 electoral votes in Republican-leaning states. The rest are all swing states.
The forecast by The New York Times has Clinton's chances even higher, predicting that she will win 272 votes without any swing states.
As for the swing states, she is predicted to win in Florida, Nevada, New Hampshire and North Carolina. Trump may win Arizona, Iowa and Ohio, though Clinton is up in the latter two states currently.
Chances of winning
Secondly, her winning chances is at 87.8% in the FiveThirtyEight polling model (Polls-only model) and 92% in The New York Times forecast. This is quite high considering that there is only 20 days into the election. With Trump's recent remarks, I think it would be quite hard for him to flip the election. Even a Trump's major PAC acknowledges that.
Regarding news cycles
The risk of news cycles turning against her isn't big, given Trump's rhetoric and line of attack. Currently, it's dominated by his claim of a "rigged" election and his lewd comments. Given the number of newspapers endorsements that Clinton has, it's unlikely that media will turn against her (fyi it's 153 vs 3 endorsements).
I do think that she has a chance to win in Arizona, but not likely to win in Texas. Texas has voted Republican since 1980, and would be quite difficult to flip the state though it isn't impossible. Check out this analysis by FiveThirtyEight about Texas.
It wouldn't be a concern that she is trying to compete in Arizona and Texas. She does have all the resources and furthermore she started the month with $150m on hand while Trump only has $75m on hand. Her campaign has a good ground game and is generally conservative.
Unless there is somehow a October surprise that is very destructive, Clinton is well on track to win.
But if you are still concerned, watch out for the 3rd debate tomorrow and see the news analysis and polls that follows.
Regarding Arizona, then assuming the polls as of mid-October are correct, and Clinton leads by six or seven points nationally it's now a swing state. There is also a Senate race taking place there this election, although it's one which the Republican candidate currently leads by a fair margin.
Texas is harder to justify as a battleground state based on current demographics and polling, but the Clinton campaign has a significant money lead over the Trump campaign, which would support running Ads in more unlikely places, particularly if it forces the Trump campaign to spend money in areas they would like to think of as part of their base.