When I said inexperienced player at this level, it was not Watcher but rather Skylord (lvl 12) and higher.
In the case of a motm, it's easy to restart over and over again for find the right path and the good deck to beat the time. But when you play a random map, it's much more difficult because our decks are not necessarily designed for this type of map : LS, Twilight, Bandit, Fire. In this case, playing with experienced players does not guarantee success.
In an ideal world, the time allotted should vary depending on the difficulty of the map. We can agree that playing a Lost Soul map with Vigil + Tower at T2 camp (Second orb) is much difficult and requires much time than a Bandit map with only grounds units at the same spot.
You realize this when you look at the rankings. Some months you can saw 5 tabs of teams that reached level 10.. and some months.. only 2 or 3 teams.
In comparison, the second most difficult level ( 9 - 4 players ) is so easy that it can be won, in most cases, in duo or solo (Treim).