I don't think you see all that may howlers in international cricket anyway, certainly the 2 decisions mentioned in the first post can in no way be described as howlers, regardless of if they were correct or not. Absolutely if the umpire has doubt he should rule not out, but then the other hand there are umpires that don't give anything and they are lambasted for that.
The thing with tv/hawkeye etc is that they dont give you 100% certainties, hawkeye is basically a guess as to where the ball would have gone, ok its a damn good guess but a guess none the less and tv replays are often inconclusive anyway, stumpings and run-outs often appear clear cut when you look at the replay but the problem there is the umpire probably only referred it because the technology is there, had it not been available he probably would have got the decision correct, its just safer to refer. The tight stumpings and runouts are just down to what the third umpire thinks at the end of the day. I've seen these decisions on TV (and am sure everyone else has) where you are sure that a batsman is safe only for it to be given out and vice versa.