Rand Pauls complaints about "selected witnesses" is odd. The Trump allies in the White House who were subpoenaed, refused to appear before the House. The witnesses who did appear were all highly relevant to the proceedings, especially the two United States Ambassadors to the Ukraine (Marie Yovanovitch and William Taylor), Lt. Col. Alexander Vindman (who was on the July 25th phone call) and Gordon Sondland (a Trump appointee who is the United States Ambassador to the European Union). Not all of the witnesses gave testimony damaging to Trump (such as Kurt Volker).
That is a lame defense. If the Trump Administration feels the witnesses were unbalanced against them, they could have allowed others such as John Bolton and Mike Pompeo to testify. They didn't want that.