initially when there was only gw : prophecies, all players were supposed to be causal, and it was, even the players in the "high end" pvp (ha/gvg) were causal,
it changes eventually when new expansions being released, pve and pvp skills list getting expanded, the skills and playing style of players have shifted from causal to a more grinding style, players cannot play causally to achieve what they could achieve when there was only gw:chap1, they need to grind in pve and pvp to get the new skills, combination, and players organisation.
random arena was categorized to be a low-end pvp arena, while HA/gvg were the high-end and later on more pvp arenas like jq/fa/ab, then players spread out wider, skills and builds are harder to get organised, the high-end pvp, namely ha/gvg became the hell ground for players to play causal, which wasn't the case when there was only chap1, and now, the high-end pvp previously, we can call it as exceeding any humanity capacity to achieve any supposed design result, or simply broken.
the low-end pvp, ra, has become the new high-end causal pvp through expansions, where the market or human can still "achieve" something in the arena unlike the broken high-end ones.
randomization can be a nice idea to make something into less hardcore, and the arena can still be high-end, however, it will demise the idea of having organised teams to pvp like the broken ha/gvg
codex has been suggested numerous times to be a test ground for bridging ra to ha, but I think the bridging is quite wobbly, because codex always require knowing so many skills with so many professions, plus having to organise players, players don't really know to do what first, randomize team can be an option, but it provides lessor opportunities for players to learn how to form groups, so it has it owns defect, which make the whole gw

vp seemingly disconnected from the whole game.
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my suggestions had been,
a) make 2 codex, one is random team, and the other is organised, with the same skill set, so players can choose want they want to learn without being drown by too many things need to be done, that is a separation between organisation of builds and players.
b) make another or change the high-end 8v8 into weekly/monthly ha/gvg tournaments with separated expansions skill, so that players without expansion will not be left out in pvp because of lack of certain skill set.
c) the old maps structure might be better?