sin's bombard got really decent after last patch so there's no such thing "lack of aoes" in terms of sin anymore lol
if you play right... bombard is the way to go in certain situations like in certain floors in mushin tower (or you could kill em 1 by 1 in stealth... your choice lol)
bombard doing really high damage now and with its hm skill... even higher.
I main a sin and they're really entertaining. it takes some time to get decent damage coz you need gear up A LOT before seeing good damage while as certain classes your base dps is quite high to begin with (fm and warlock for example...)
I have almost every class in game, well have all of them and very few that aren't yet lv50... lv1 destroyer that I really debate if to bother with her or not *_*
anyway ~ I have a summy and she's kinda undergeared atm lol working on it o.o
she's sunflower build as many sums are.. and the dps is quite high o_O
+with the right cat build... you don't need much.
still lacking some skill points but she's not yet 50 so it prolly will get even better when she will be 50 (she's 1 lv away from 50) working on getting her accessories to oathbreak as well ...
I'm no expert on sum and despite the fact I been playin quite a while with my sin I'm not expert on sin either, in fact I'm just getting to know them better as I play with my clan both pve and pvp and I'm still learning how to get better dps in certain situations how to evade more efficiently (that depends on your PC/net connection :c )
BOTH these classes are good and both are easy to farm stuff in theirown way.
sum is easiest but sin is higher dps (I could be wrong since my sum is not anywhere close to my sin's gears lol)
both can be really good solo pve and pvp...
in tag matches... 6v6... you name it.
just need learn and practice your skills and combos.
learn how to counter best each class some requires different skill builds or lil changes in your spec to counter better
I really love my sin but in certain situations or if I wanna farm certain items fast - sum would be a better job in terms of how hard/easy things can be with a sum compared to a sin and vise versa.
overall - both classes really good solo play you just need gear up and learn how to use your cat/poison best ^_^
it really depends which you think you would like better, try them both and see if you like sin or sum better