Of course what we judge to be "centre" or "extreme" is very subjective. I don't consider Alberta's NDP to be centre left for a few reasons.

First, "2 points" might not sound like much, but it's a 20% increase in corporate tax rates, at a time when we're probably going into a recession or close to. However mildly, the NDP is looking for traction in anti-business sentiment in the province - its platform is full of allusions to businesses taking advantage of Albertans and not paying their way. Businesses should pay their share, fair enough, but at the end of the day they're the ones that create jobs for Albertans, and if even just a few companies go under because of tax increases or more general hostility towards the, these NDP positions will hurt more people than it helps.

On not "taking over the oil patch", I suppose that depends. It's not clear what they want to do to royalties, but based on the things they're saying an NDP government would probably seek to raise them fairly dramatically, which would probably have a significant effect on new energy projects starting in the province, particular in combination with the current oil and gas prices. And based on their promise to increase upgrading in Alberta, they'll have to interfere with the industry in some way, and they'll essentially be telling oil companies how to do their jobs.

And on balancing the budget, I doubt you'll find any instances where the NDP is calling for cutting expenditures or doing things more efficiently. They would, however, like to spend more on services despite Alberta already spending more on health and education than any other province. Their solution to the budget gap is to raise more money through taxes or royalties. Both the Liberals and Conservatives (or Alberta Party or PCs) are willing to approach the issue from both sides, but the NDP doesn't appear to be.

All this while being deeply sympathetic to labour unions (which were the party's roots, after all).

Notley made some great points in the debate. But that doesn't change the basic fact that the NDP is significantly further left than the Alberta Party, let alone the PCs, on most important issues.