In laning phase, you have 3 options with shen depending of your matchup. If you are good with shen, you can be very agressive with your trade early ( Taunt+ Ki Strike With your Grasp proc then fall back with shield then sustain youself with your q on minions for the next trade). You can do that when your opponant go for a cs and you have more minions than him. 2nd Options is to poke with your Q forever and only trade when your opponant come close to you. 3nd option is poke but being very passive and AFK farm while you are scalling and wait for your jungler if he feel to gank your lane. Once lvl 6, this is where shen shine most of the time. To play shen, you need to understand that its not just to be a meat shield tank... his ult exist to turn an agression into your team favor.
I Do agree, laning with shen can be tricky because of his lack of inate power, just keep in mind your Q is your bread and butter and you should always poke with it. However, there is a point where he become so tanky that you can split push and the oppoant need more than one to stop you ( Not that you cant kill him 1vs1, it take time to kill a tank tho...) You can dash through the wall and escape some situation easily.
By the way, Shen can deal damage to a squishy. He have a burst damage, not aoe. Give him titanic hydra with trinity, thormail and sunfire cape and your adc is probably gone if he combo on him. ( Taunt-Hydra-Sheen-Kistrike-Grasp-Sunifre-Thormail-deadmans ) after that, you cant do shit till your taunt is online again.