Deontological ethics is a form of Christian ethics. Christian ethics encompasses duty, to be sure, but it also encompasses telos (e.g.,--goal--the Kingdom of God, the glory of God) and motive (e.g., heart purified by faith).
Deontological ethics (or normative ethics) is a very important aspect of Christian ethics and is sadly being downplayed, even by many in Reformed circles. But no, it is not the whole of Christian ethics.
I'd say it involves the main three: deontological, teleological, and existential.
Jesus frequently condemned mere outward conformity to the law. The actions of obeying the right standard should spring from a right heart (motive) and have the aim of glorifying God (goal). We can see that Standard, motive, and goal conform nicely to what I caleld "the main three."
So, it is not just "doing the right duty" but doing it for the right goal, and for the right motives.
But, standard trumps the other two in the sense that the motive and goal must be brought into conformity with the norm, but then again the norm tells us about the right motives and goals.
Bahnsen teaches that Christian ethics requires the goal, motive, and standard. Each one is necessary and each one is sufficient. When all is said and done they are equivalent to each other. One cannot take a motivational approach to ethics and leave out the norms and goals of ethics. The same goes for the other two. The goal, motive and standard all require each other in Christian ethics. These three perspectives all end up saying the same thing because God does not give us three competing systems of ethics in the Bible. We can approach it from three different angles, but there is harmony and the conclusion is always the same.
BTW - I don't pretend to be an expert in this field. I didn't realize J and PM had already responded while I was responding. Just listen to what those guys say. They know whereof they speak.
For example, we are called to "love" and that "love" fulfills the law. Yet "love' is not vague and content-less, but is defined by obedience to God. Jesus said in John "if you love me you will keep my commandments."