Degree is not rank and you must see that they aya refers to the situation of divorce and the fact that the woman, if she believes in God, should not hide pregnancy. It is not setting ranks. Draja in the Qur'an is never a rank but an specialty. Prophets have different missions, and the Qur'an says that saying they have different daraja. But sets not rnaks within them. In this case the daraja is of responsibility and duty. If the woman is pregnant upon de ex husband revolves the duty to attempt at reconciliation if it is possible, and if not, the duty to provide for the child and the mother.
Also, see, that it would be ridiculous to set and different rank where it says just before that to them (feminine plural) same as against them (feminine plural), if this istrue it cannot be negated after saying the opposite, so it is not a question of ranking but of the specificity of the conditions.
Concerning the witnessing, As shown, quite wisely by the way, by Ale Asghar Engineer, who a short time ago, the outlook in Qur'an respecting women and men differs in that women are considered from the point of view of their (of the women) rights and men from the point of view of their (of the men) duties.
So the question of the witnessing that you put forward as far as I can see stems from the fact that it is not voluntary witnessing but that the witnessing is imposed. It is an obligation. Of course the witnessing by women must be accepted just as the witnessing by males, but they are nto to be obliged, in this case since it is an obligation, in orde to soften it and make it easier it is proposed what shown. It is in a setting where obviously it may not be easy to get capable witnesses.
The ridiculous attempt to disqualify women as witnesses is not the product of Qur'an but of the malecentric mentality, which if it does not cling to that would cling to something other. Where there is a will there is a way. No scripture will stand in the way of pride and self-delusion. And in order to bring the Qur'an in true light as the Qur'an itself says, you must be of pure heart.
Salaam