In my experience of a player going away and back again from the game, the dungeon limitation was always an issue.
As a casual, you will find yourself out of coins and needing a 2nd and 3rd toon everytime you have a spare time, like weekends. And for a casual it's a great issue, because u barely will have 1 toon in "endgame" equipments. Wich will make you have to run your alts only on low dungeons and get frustrated due to lack of needed drops for your main gear, or even low profit.
The game should not limit how much we want to play with our characters.
The tank and healer problems are partially due to it, casuals can have 1 endgame toon, more than that is an exception, and if they are a tank - like me - or a healer, this will means that your endgame party will have them for like 5 (or less) runs on a weekend or holiday.
