The Beast Within 
This question is easy and complex all in oneā¦ just as worgen are man and wolf in one. Yes, worgen are always full of human logic and beastial instinct. This is the way it was designed, and how it functions to this day. That does not mean, however, that the two must be in conflict.
Worgen Origins
The origin story goes all the way back over nine thousand years, to wolf druids who used the four-legged Pack Form. It was pure wolf (not wolf-man), and the druids often lost themselves fully to wolf instinct. While it was the most powerful weapon against the satyr horde, it was also too hard to control. Those druids prayed to Elune - the goddess of Balance - for an answer. Elune answered, turning the wolf druids into wolfmen. It was neither manā¦ nor wolfā¦ but the perfect balance between. This is an extremely summarized version of the whole origin story, described in the five part comic series Curse of the Worgen.
What is ābalanceā?
Worgen are the perfect balance between Man and Wolf. Even the Nightbane and Bloodfang are intelligent enough to wear clothes, use magic, build, speak, read, write, form government, have religion, and shapeshift (Duskwood, Dark Riders, Curse of the Worgen). And even the most ācivilizedā of worgen must sate their need to hunt, feel the call of the wild, and the need to run in the wild. As seen in Wolfheart as Genn Greymane and his noblemen run and hunt on all fours to dig their teeth into Teldrassil boar, and by Anduin in Before the Storm appreciating that a worgen army can feed themselves.
Sometimes, the human and wolf parts of the worgen mind are in conflict. This is described as a worgen without balance, and are often incapable of shapeshifting. This is where the Ritual of Balance comes in. It is not a cure, and some people can shapeshift fine without it. What it is, is kind of therapy. The ritual is a series of visions, which inspire you to move on from your past and get over your own rage, and then to harness your rage into fury. Not eliminate it, mind you, but harness it. (Halford Ramsey Curse of the Worgen, and Varian Wrynn Wolfheart)
If the man has accepted the beast, the beast will accept the man. The result is a ābalancedā worgen. One where the human logic and wolf instinct run hand-in-hand, like a beastmaster and his wolf. Even in human form, Genn Greymane will psychologically never be fully human, and this is depicted with his bouts of rage ingame, in Wolfheart, and in the upcoming novel Shadows Rising.
Conclusion
So to answer your questionā¦ worgen are sentient beings with beast instinct. They are both. There can be conflict between the man and wolf, like ying and yang, but a worgen is at their best not when one is suppressed, but when both work as one.
Curse of the Worgen
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Lord of his Pack
He ran toward the starboard side of the ship, full speed. The wet deck didnāt affect his balance: he was singularly focused. The animal instinct inside him coursed through his veins. His mind was hell-bent on the act alone, nothing else, just the doing. And then, as he reached the railing, he jumped!
Wolfheart
The lupine figures held their ground, although there was in them the evident urge to run, to hunt. They did not turn from the gazes of the crowd, instead staring confidently back.
Knaak, Richard Aā¦ World of Warcraft: Wolfheart (p. 209). Gallery Books. Kindle Edition.
