For the amount of times you actually lose him without getting to fire, (which is low) it is shruggable. 10pts is not a big deal, if it only happens every other game or so... I want to fail the leadership test and run away anyway. Sure it would be nice to keep him, but if he takes a few power hits from a challenge, he probably saved the squad (at least from THAT power weapon.) The squad will regroup automatically if they make it away to safety anyway.
Meltabombs are insurance, you either pay for it or you don't and take your chances. I like to place Meltabombs on higher initiative IC's, where they can potentially take out dreadnoughts (like the Death Company dread with blood talons... yikes!) or on sarges when using the last of my points to fill out my list.
If I was to take an assault squad, I would go lightning claw or thunder hammer, depending on my IC. They are made for close combat.
I agree that tacticals (besides the sarge) are weighted to the shooty side, and a power sword would all rounder them. But I find more of my opponents to be of the assault sort, where my power weapon would be mostly out classed in my small combat squads. For the enemies that are shooty, the power sword is unnecessary most of the time.
If I ran full tactical squads against assaulty armies, I would agree with you completely. Except for one thing... Precision Shots. The plasma pistol may have a place here, as it allows you potentially kill a character or special and still charge. Probably too many eggs in one basket to buy both a plasma pistol and power sword, but it would be very fun to play.