You described what Mercury/Pluto was like: it's speech that's too intense, too determined to make the other person listen and believe what you say, and agree with you. The nature of Pluto is to overpower. This means you can take everything to extremes (fire or ice) and you can possibly be a bit intimidating as a result. Pluto is the planet that rules Scorpio and having your Sun and Venus also in that sign means you do nothing by halves, you have to go the whole hog. In the many power struggles you'll have, you're determined you will be the winner. It's not like Libra, who likes the scales to be evenly balanced, it's wanting the scales tipped to your side.
On the plus side, Scorpio means you are not a quitter. Whatever you put your heart into, you'll stick with it to the end, till your aim is achieved. It also gives you considerable depth. You're not a skater over the surface of life, you'll want to break a hole in the ice and plummet into deep waters to find out the hidden things lying underneath. You'll enjoy meaningful conversations, not trivia. Nothing will be off limits to your questioning mind.