[Avodah] Avodah] Saying Tehillim for a sick person

[SBA]

From: Dov 
It always surprises me when kehillos that rush their weekday shacharis make
such a big thing out of the passuk-by-passuk recital of Tehillim for a
choleh at the end, the mispallelim shockeling with furrowed brows as if to
say, "Aha, now we're really davening!"  What have you been doing for the
past 30 minutes?! 
>>

That's been puzzling me too. Why not suffice with Refoeinu -adding the Yehi
Ratzon - a tefilah compiled by the AKHg -  which surely has all the
ingredients/segulos required for a refuah? And having said that, what's the
point of adding 'man-made' Tehillim?

I have the same question regarding the Vidui said (at least in nussach
Sfard) after ShE. Isn't the AKHg's "Selach lanu " enough? 

I am sure there must be answers to this and would appreciate hearing them.

SBA