The question is very interesting, and it is also very hard because we don’t know what should be “acting strictly according to Russian national interest”.
My sense is that despite all the admiration we may have for Putin in Syria he is damaging Russia’s national interests on two points:
a) He has an economy based on large companies sucking the country dry and he is not grooming SMEs and real private entrepreneurs. These companies are largely based on natural resources just like the old Czar landowners relied on agriculture. Over 30 years of Chinese development were based on SMEs and real private entrepreneurs, followed by SOEs, but not the other way around.
b) After taking Crimea someone else should have gone out of his way to find a compromise on Ukraine. This didn’t happen, or not to the extent necessary. I think this is because the large number of modern “Russian serfs” of great companies, with little or no hope to improve their livelihood, need nationalism to find a motive in their dire predicament.
I daresay that this is against Russian national interest. Putin should have a bold program to cut down large companies and promote real smaller competitive enterprises. But perhaps he can’t do it because large companies are the best and most effective support of his authority. The power and arrogance of these large companies, mixed with a good dose of racism and nationalism made so far impossible for instance to come to a fruitful economic agreement with China, despite the official political necessities of both.
This is dangerous for him and for anybody else in the long term.