The only thing we differ seems to be what we think is the intention of the original post.
knightkrawler wrote:As for how I offer heroes to players and how we handle death...
As much as I understand, the original purpose of the master class heroes is not to be used to replace the former hero after his death (as normal), but to replace a still living hero in case there are not enough players to make a full party of four. The master heroes are stronger than the standard ones in order to compensate for the missing party members.
In this case, and only then, I would rather use the standard heroes, or whatever heroes the players are using in the running campaign, i. e. the still living hero of the player, and not some stand-in hero for one quest. If players then feel the need to somehow compensate for the missing heroes, they can do so by different means, including modifying the quest. It's still better than replacing still living heroes.
If a hero acrually dies and is to replaced by a new one, or at the start of a new campaign, there's nothing to say against the master class heroes, if only to have some variety.