It depends a lot on what endgame content you mean and your personal playstyles/preferences. The best class stats wise won't necessarily be your best.

Solo- it really doesn't matter. Play the class you find the most fun.

PvP - sorc/sage is considered to be the best, but both soundrel/op and merc/mando are fine for unranked

PvE - all heal classes are viable. I think numbers-wise scoundrel/op have the highest potential but it's not a whole lot different from sorc/sage. Merc/mando are mediocre heals, but good if you need extra dps.

Personally, I stick with scoundrel/op healers, but that's more from the benefits of being a stealth class than for the healing performance. (using combat stealth to avoid repair bills on a wipe or to reset the medpack is useful)

From my exp Sorc is best overall for all content, solid single target and AoE. Second would be Operative coming in with best AoE overall but less single target. Last place is Merc with solid single target but comparatively poor AoE. Unfortunately AoE is kind of a king maker so Merc loses out.

Personally I think Operative is the easiest to play. Sorc is a bit more involved with knowing when to regen force and how to use abilities correctly.

So I would recommend either Sorc or Op depending on which playstyle appeals to you more.

From my exp Sorc is best overall for all content, solid single target and AoE. Second would be Operative coming in with best AoE overall but less single target. Last place is Merc with solid single target but comparatively poor AoE. Unfortunately AoE is kind of a king maker so Merc loses out.

 

Personally I think Operative is the easiest to play. Sorc is a bit more involved with knowing when to regen force and how to use abilities correctly. Stealth rez as an Operative isn't usually a viable idea as leaving HOTs on raid members will pull you back into combat so it's only very situationally useful.

 

So I would recommend either Sorc or Op depending on which playstyle appeals to you more.

Personally I think operative is more difficult requiring an upkeep of HOTs and anticipating incoming damage - sorcs are primarily reactive healers and thus better for people with less experience.

Look at the new healing parse leaderboards. Roughly speaking, here's how the classes rank in terms of single target/AOE healing from best to worst -

Single target - Op, sorc, merc

4 targets - Op, merc, sorc

8 targets - Op, merc, sorc

Single target as an operative during a boss fight however is a little less viable than sorc especially for unscripted spike damage going out. This is because it's unviable to keep probes on every single raid member so one would have to apply probes first before bursting them up.

As a sorc healer main, I feel like AOE healing is like pulling teeth with relatively weak AOE abilities - if a whole group takes raidwide damage, I can pick them up... in 1.7 seconds without any Surge buffs, and it's not an instant heal - it's a HoT ability. I've been able to heal best when pre-empting scripted damage and precasting accordingly, like watching boss casts and parse timers - a bit like the Operative but at least it doesn't involve a constant upkeep of kolto probes. Force management is fine as long as one knows where to spend Surge buffs from Innervate on recovering Force (like in a spare moment when everybody's gucci at 100% health) or a reduced cuddle puddle cast.

I think merc healing is the easiest. It has very good AOE, although not as OP as operative AOE and is in general, a reactive/burst healer barring kolto shells which last forever. It can burst up a single target faster than a sorc can cast Dark Infusion if the Emergency Scan + Healing Scan insta proc is not on cooldown, but otherwise bringing someone up from near-death with nothing but Rapid Scan and/or Progressive Scan if you're that kind of person is going to take a while. There are also a few utilities specific to certain fights that make it more preferable like Hydraulic Overrides for Revan and reflect for, well, a lot of things.

which class is the best healer, what i mean is which is the best for mobility. Or does that not matter in the end game content. I know you get good healing from the sorcerer / sage, but i want to try something different, so i would appreciate your thoughts.

Operative/Scoundrel has the most mobile healing spec, but probably the most difficult to master. They also have scamper/roll. If I were rank the three healers, I'd put Op/Scoundrel and Sage/Sorc heals tied at first, with Merc/Mando 3rd. Merc/Mandos are slowwwwwww but are incredible single target healers with great DCD's.

Like what people before me have said it just depends on your personal play style, and what you need in a group but based on numbers this is what’s best for what (my personal opinion)

PVE - Opertions - Merc Healer, it has great burst great aoe healing and does good off dps

PVE - Flashpoints - Opertive, great group healing good enough burst healing for fp and has stealth is always good in a

FPs.

PVP - Regs - All are about equal but sorc is easiest

PVP - Solos - Sorcs - Mainly for the mobility

PVP - Group Ranked - Fighting against pressure is Opertive, going against swaps sorcs are best.