First thing try to gain enough shards to get Druid or at-least use Angel for now. It will be good if you have Angel already and quite leveled (if not go for it) as healer in raiding will make a big difference (this is what I tested myself too as others suggested).
Also you have 5 good good 4-star heroes (assuming Assassin lvl 60 is 4-star) which is nice but do level them more. I would recommend add Angel and for raiding keep top 4 as it is and replace Assassin with Angel as healer.
And you definitely need Druid, do skull dungeons which will give you shards and will also give experience to level your heroes. As most of them are not legendary thus you need more upper levels for them.
Also consume your crappy heroes as they are all adding in your might. Like Shaman is completely useless but Marksman can be used in raids as range but I prefer Engineer more than Marksman.
About your might its a bit high but I don't think its too high. Also increasing heores level will increase your might but consuming unused heroes will decrease it and heroes are the ones around whom this whole game revolves. Like I was at 6K+ might then I consumed my 7 extra heroes and brought it down to 5K and then upgraded my legendaries to higher levels (still in 4-stars) and my might now is 5.6K again and increasing. But I can raid 80% of bases at 100%-victory with my heroes alone and for remaing 20% I sometime uses my troops (I have lvl 2+ troops in tier-2 but I still prefer tier-1 troops as they are quicker to train and they are there to support my heroes only).
I hope this long reply will help you a bit.