both sides are making a point here. The +5 rule isnt entirely off the table, i find its part of the art to find the right mob where it applies, but by no means it applies to all mob and is probably very dependant on your own pro standings and activities. Fast weapon speed seems to be a big factor in the question if you get hit or not, maybe even a certain smooth hunting-rythm with slower weapons, that seem to deflect dmg better.
Also mob werent born all the same day, many got changed over time. There are probably as many different mob generations as item generations out there, both kinda seem to reflect each others aspects, resulting in the balancing of the game. And i am absolutely sure that mob-level does not solely reflect hit level of the mob, there are tons of aspects integrated in mob-level, strenghs and weaknesses like speed, aggro range, hp, size, dmg type, fast regeneration and such.
The mobs with equal hitlevel and moblevel are probably those which are best to read for the player and they seem to be the most popular. Many players share that part of the way up, but the curve will eventually change out of the players spectrum, he will grow out of that mob or the size of it.