Having insurance is way better than not having it..especially if the coverage is good with very small co-pay.

I don't think it's uncommon for employees to pay a percentage of their ins--I've heard several people talking about 'their part' being 50%..so 25% doesn't seem overly bad to me.

Insurance rates are going up and there are a lot of changes being forced on ins companies at the moment.
I think it would be reasonable to view your company's new thing about you paying part of the premium as being their way of trying to not get gouged by sudden price hikes..unless you have other information.

If you keep insurance now, it will be easier to have insurance later if you need it--even if you need to switch providers later for some reason.

That's my semi-informed opinion and may or may not be worth anything.