No it is not literally balanced, the idea was designed to be realistic, long before the introduction of the geode system. The fact that geodes came later on is an entirely separate matter. I do not feel that more weather should be added simply for trials if it draws away from the realism of the game. (Bare in mind light weather is just as rare if not more so.)

Do not take that the wrong way I still think an alternate means to obtain geodes should exist. Openly available battlefields, that contain geode/rite dropping enemies with all 8 weathers, or something of the like. Do also consider the balance associated with such an addition. Adding a location with unlimited weather would make trials with matching monsters much easier, meaning combinations would have to be carefully looked at. Also, such a thing would make no change to either the 5 minute wait time or the fact rites will replace a geode drop. It would mean that one area 60+ and another 80+ would have to exist in order to prevent undermining itself. As it stands at 5 minutes a geode even under perfect conditions a player is looking at 275 minutes or ~4 1/2 hours. In easier terms I'm saying by all means level the balance between frequency of all weathers, just don't do it in current areas and don't expect a magic turn around from the AH. (Note the price on wind geodes is also rather high and wind weather is common enough 1 per 5 minutes is possible.)