Well, I mostly agree on lucky board.

But, don't forget the word 'lucky'. How good the event lucky board turns out to be, depends on your luck.
If you can spend a lot on it, can expect the average return will be pretty good compared to other events. But if you are a small spender on lucky board - then let the luck decide the event's worth, its that simple.

Personally, I don't prefer lucky board too much. Yes, I do spend there, but only on last day, after looking at the rewards of next week. Why? well, its just me, but I like to focus on things instead of diverting it everywhere, as my coupon sources are limited(right now, trying to upgrade refine and tactics). Random rewards like - 3 seal frag, 5 summon frag, coins, cultivation runes, lvl 2 megatama etc doesn't do me much good. And due to my bad luck, those lucky boxes most likely gives me coins or lvl 2/3 megatama box, or advanced thread/cloth which I have no use of.
So basically, it depends on your 'luck'. If you get some lvl 4/5 mega - then yes, it can be a decent event for you, especially if you want any of the redeemable rewards.
Bottom line:- Do spend cps on lucky board, but don't go overboard there.

In general I try to save for sage treasure or some other events where rewards are good for me. For example:- Last treasure key event, managed to get 100 med refines. Those were a pretty sweet deal giving med refines at about 17 cps/refine, so grabbed all 100 of them by collecting free keys and then dropping another 800 cps.