Bob Dole was a boring speaker because his speech lacked inflection. Pronounce all syllables. You will sound more professional when you do. Missing syllables make for sloppy, lazy speech. Keep the vocal energy flowing.
Energy is the key word to speaking effectively.
Fading away or dropping ends of sentences will leave the listener in the dark. If the point is important enough to be made, it's important enough to be heard. Learn to know your voice. Once you've identified the habits you want to eliminate you'll be on the road to developing habits that will make you an effective speaker. As with anything else, it is possible to improve how you speak.