Opinions from a beginner so you milleage WILL vary =)
I took my lvl 14 CHA/CC/Heal based Spellsinger to Lamannia and LR'd him. STR 18 DEX 08 CON 16 WIS 08 INT 08 CHA 14, level ups in STR. Same feats he had but took Maximize instead of SF: Enchant and Power attack instead of Heighten, traded every CC spell in his spellbook for a utility/buff alternative. Effectively I traded CC/DCs for STR/dmg. Got Spellsinger II too obviously. Didnt change a single item in his equipment.
What I can say is that in areas/quests where before I had to be very careful and really worry about not using all my SP, now he can just enter, buff and rush. More survivability (due to MUCH faster killing), more improvements for the party (spell slots not occupied by CC spells, more SP for healing, etc) and definetly a better sense of contribution. Not that I personally didnt/dont like CC, but my limited experience in parties tells that CC is good to have (as most things are) but absolutely not a must. And by reading the forums I believe CC in epics is restricted to Irressistible (no save), Fascinate (no significant change in my DC) and spells that dont belong to the bard spell list (mass hold, mass comand, etc).
All in all I am happy, he can heal better than before, fight better than before and that darned oversized kobold in Mired In Kobolds will not laugh at the lonely bard entering her hoard chamber anymore ^^ (tho the second dragon still has bragging rights and at least 45% HP left...).
PS - Would love more experienced advice on the Empower Healing + Empower/Maximize. Which combination makes for more cost-efficient heals at lvl 20? Is one or the other (or both) particularly useful or a must have for parts of the game I havent experienced yet? Thanks already