hmm true to some extent, i haven't played enough 2v2 to be able to verify.
Yeah I think it should be tested, but I reckon it is nearly impossible that in a team with 2 you have good units versus all of the levels, for example 16, 17,18,19 and 20. Perhaps huge tower luck can save you, but else there is always one round that you will leak hugely if the enemy sends. This is no problem if you do not mind the 'impossible kill'-factor, but I am no fan of it. But again, it needs to be tested to see if this is true.
The same for your question if it washes each other out. If either of the two weighs in slightly more on the game it can be a huge influence. Not for nothing are we playing version 3.41. A lot of adjustments and balancing had to be done to get to this version. Playing with half the players is a robust change which will no doubt influence the balance (and probably for the worse).
As for my 'king argument': take the game I played last night versus you. I was going elite archers and I upgraded the king to 30-20-20 pretty much alone before 14. If every player leaks 10 units, this will mean the 30-20-20 king will have to fight 40 units in 4v4, but only 20 in 2v2. The king is therefore relatively twice as strong in 2v2. (However, in many cases you cannot upgrade the king alone, and then the extra wood you have to invest with the 2 players to compensate for the two missing players add another dimension - which shows the difficulty of the balance)
Finally, one more thing: the luck with the towers plays an important role in -hpgmcb prophet-legion. This luck factor becomes less important if there are more players - with 4 players you can expect 1 to have good towers, 1 bad, and 2 mediocre (for example). In 2v2 the differences can be way bigger: it is not uncommon for 2 players to get 2 good towersets, which means in 2v2 that the entire team has good towers, the enemy 2 bad towersets etcetera.
What this means is that the luck factor (which is already present in 4v4 and 3v3) will be even increased, both in games and in the rankings. I think that's not a good idea for the LIHL, where we (or at least I) want games to be played (as much as possible) on skills.
I agree that it is sometimes frustrating to not be able to play a game when there are just 5 online or so. But I think the primary concern for this league is fair and fun games. It is really doubtful the games are fair because of the three reasons I mentioned (sending, king, increased luck factor). This will probably also influence the fun in the game and the 'authority' of the league ("the league is imbalanced because of the 2v2!"). I think this outweighs the discomfort of waiting.
However, I will once again stress that this is (informed) speculation, and if testing shows different results I am not against 2v2. But without more information I would still stick to a 'no'.