I'm afraid you can't do this without subquery:
select
sum(a.Value1),
sum(a.Value2),
sum(a.Value3),
sum(a.Value4),
sum(a.Value5),
stuff(
(
select ',' + t.c.value('.', 'varchar(400)')
from table as b
outer apply b.[Xml].nodes('r/p') as t(c)
where b.[DateTime] = a.[DateTime]
for xml path(''), type
).value('.', 'nvarchar(max)')
,1,1,'')
from table as a
group by a.[DateTime]
BTW try not to name your columns as types in SQL Server.
sql fiddle example with simplified data